I finally decided to rate all the hops I have experimented with for dry hopping as well as give a description of their flavor and aroma. I originally got the idea to compare dry hops from scottland who bought a 12 pack, popped the tops, added hops, and recapped. I tried that a couple of times, but the carbonation got in the way. There was also a lot of hop dust. What I ultimately ended up doing was to save the beer from my starters and add the hops for a secondary fermentation so to speak. Then I would strain out the hop dust and bottle them. I tried many dry hops head to head in my quest to find the best hops for my IPAs. For the most part I will rate hops on a scale from fruity to dank with the following terminology: fruit, citrus, pine, spice, dank. A lot of people try to describe hops with other fruits or food items, but those 5 terms sum up most of it. There are a few hops that do have a unique flavor, and I will mention that. The hops are listed in order of my favorite.
Centennial - Fruit, citrus, and a little pine with a clean great taste. Smell is similar, but I feel it tastes better than it smells.
Citra - Fruit and citrus, they don't call it Citra for nothing. It also has a very strong citrus aroma.
El Dorado - Very close to Citra with fruit, citrus, and a little pine. Doesn't have the smell of Citra though
Simcoe - Pine and citrus with a little fruit. Some people say this hop is dank, but I would say it is the epitome of pine. Has a pine marijuana smell.
Galaxy - Citrus and fruit. Great smell. Very close to Citra, but has a slight bit of sour that all Southern Hemisphere hops seem to have.
Falconers Flight - Citrus, fruit, and pine, with a little spice. This is a blend of different hops, and it certainly has Simcoe, CTZ and other NW hops in there.
CTZ - Pine, citrus, dank. This is a dank hop, but it has an incredible amount of pine and citrus taste. The smell is similar, but not as strong as Simcoe.
Stella - Pine, citrus, fruit, and a little spice with the slight sourness that I find in Southern Hemisphere hops.
Bravo - Light fruit, pine, a little spice, but very smooth and clean. Surprisingly good for a bittering hop. The light fruit taste is very similar to Amarillo, but IMO there is more going on with this hop.
Mosaic - Fruit and pine. Nice, but overrated, not that strong. This was bred from Simcoe. I would advise saving your money and mixing Simcoe with another hop because I don't think Mosaic has a particularly definitive taste to justify it's price.
Amarillo - Light Fruit. Good aroma. Taste does not match aroma. Another overrated hop IMO. While Amarillo is stronger than Cascade, every top beer that uses this seems to mix it with Simcoe (Vinny from RR says it isn't good by itself). I just think all these great beers started doing that and since Amarillo smells great and is expensive people think it must be worth the price, but it really isn't definitive by itself and I'm not sure I could identify it over Cascade in a mix.
Calypso - Light fruit and pine. Nice, but not that strong.
Green Bullet - Fruit and spice, a little sour.
Cascade - Light fruit and citrus. Nice smell. Not that strong compared to other hops that are commonly used in IPAs, but pretty decent for the price.
Zythos - Citrus, fruit, pine, spice, and dank. A blend of hops, strong smell, but I'm not a big fan of the spice which most likely is coming from Chinook.
Kohatu - Citrus and fruit, with a fair amount of that Southern Hemisphere sour taste.
Warrior - Dank, citrus. Not much smell, but a clean light taste. Warrior is known as a clean bittering hop, so it doesn't have a heavy taste as a dry hop. I'd personally just use less CTZ if I was going for this taste.
Nugget - Dank, spice, and fruit. Nice aroma for a bittering hop.
Galena - Light citrus, spice, not strong. This is also known as a clean bittering hop so it doesn't really provide much as a dry hop.
Nelson Sauvin - The BEST smelling hop. Stronger aroma than Citra. It has a very funky taste that is extremely definitive, some weird aspect of that sour Southern Hemisphere taste. It is probably the most unique and definitive hop I have used, but I don't like that funky taste. Stone Enjoy By apparently mixes this with Galaxy for a double dry hop. I can totally smell and taste the Nelson Sauvin as I rated Enjoy By a 5.0 for aroma and a 4.5 for taste.
Sorachi Ace - Citrus and spice. Not that strong and the spice is a little weird. A little bitter and grassy as well.
Kent Goldings - Light spice and pine, not very strong, English hops aren't really known for being great dry hops.
Magnum - Light spice and fruit. Not much taste. Another clean bittering hop, doesn't contribute anything particular as a dry hop.
Millenium - Light spice and fruit. Not much taste. Very similar to Magnum, but possibly lighter.
Williamette - Light spice and a little fruit, not strong, more spice than Kent Goldings, not worthwhile for an IPA but could contribute something interesting in a different style of beer.
Polaris - Dank, spice, citrus, fruit. This is a strong taste but the dank and spice overpower and don't mix well with the citrus and fruit. A bit sour as well.
HBC 342 - Fruit, citrus, and spice. A very weird spice taste similar to Sorachi Ace. A little sour as well, although it really isn't that strong as a dry hop.
Apollo - DANK. This hop is as dank as it gets and has a sour taste by itself. When I tried mixing it with other dry hopped beers at the time, it overpowered them. My friend and I did not like this at all, it was so bad we had to dump it, but it might have been good if mixed at 10% as the Heady Topper clone uses ~10% Apollo in their dry hop mix and the taste is not so definitive there. If I hadn't used it successfully in my Heady Topper clone, I would probably rate it worse than Chinook.
Chinook - Spice. This is a definitive spice taste that can mix well with other hops, but by itself it's just a bitter spice taste. Probably the least liked of the C hops, and the most likely hop to give the dreaded cat piss taste.
EDIT: All these reviews are based on dry hopping a beer that had no hops in the boil. While many hops have a similar taste in the boil, even for bittering, some hops that are great as dry hops aren't so great for bittering and vice versa. For instance I can totally taste CTZ if used as a bittering hop, even behind a bunch of strong late addition and dry hops, as in head to head batches other bittering hops gave a much different flavor even though I used the same late addition and dry hop schedule. On the other hand Apollo is a great bittering hop and doesn't give a sour taste at all as a bittering hop, while Polaris does. I also did a SMASH that was FWH with Citra once, and while it wasn't bad, I imagine I would have liked it better if I used CTZ or Apollo for a bittering hop and kept the same Citra late additions.
Centennial - Fruit, citrus, and a little pine with a clean great taste. Smell is similar, but I feel it tastes better than it smells.
Citra - Fruit and citrus, they don't call it Citra for nothing. It also has a very strong citrus aroma.
El Dorado - Very close to Citra with fruit, citrus, and a little pine. Doesn't have the smell of Citra though
Simcoe - Pine and citrus with a little fruit. Some people say this hop is dank, but I would say it is the epitome of pine. Has a pine marijuana smell.
Galaxy - Citrus and fruit. Great smell. Very close to Citra, but has a slight bit of sour that all Southern Hemisphere hops seem to have.
Falconers Flight - Citrus, fruit, and pine, with a little spice. This is a blend of different hops, and it certainly has Simcoe, CTZ and other NW hops in there.
CTZ - Pine, citrus, dank. This is a dank hop, but it has an incredible amount of pine and citrus taste. The smell is similar, but not as strong as Simcoe.
Stella - Pine, citrus, fruit, and a little spice with the slight sourness that I find in Southern Hemisphere hops.
Bravo - Light fruit, pine, a little spice, but very smooth and clean. Surprisingly good for a bittering hop. The light fruit taste is very similar to Amarillo, but IMO there is more going on with this hop.
Mosaic - Fruit and pine. Nice, but overrated, not that strong. This was bred from Simcoe. I would advise saving your money and mixing Simcoe with another hop because I don't think Mosaic has a particularly definitive taste to justify it's price.
Amarillo - Light Fruit. Good aroma. Taste does not match aroma. Another overrated hop IMO. While Amarillo is stronger than Cascade, every top beer that uses this seems to mix it with Simcoe (Vinny from RR says it isn't good by itself). I just think all these great beers started doing that and since Amarillo smells great and is expensive people think it must be worth the price, but it really isn't definitive by itself and I'm not sure I could identify it over Cascade in a mix.
Calypso - Light fruit and pine. Nice, but not that strong.
Green Bullet - Fruit and spice, a little sour.
Cascade - Light fruit and citrus. Nice smell. Not that strong compared to other hops that are commonly used in IPAs, but pretty decent for the price.
Zythos - Citrus, fruit, pine, spice, and dank. A blend of hops, strong smell, but I'm not a big fan of the spice which most likely is coming from Chinook.
Kohatu - Citrus and fruit, with a fair amount of that Southern Hemisphere sour taste.
Warrior - Dank, citrus. Not much smell, but a clean light taste. Warrior is known as a clean bittering hop, so it doesn't have a heavy taste as a dry hop. I'd personally just use less CTZ if I was going for this taste.
Nugget - Dank, spice, and fruit. Nice aroma for a bittering hop.
Galena - Light citrus, spice, not strong. This is also known as a clean bittering hop so it doesn't really provide much as a dry hop.
Nelson Sauvin - The BEST smelling hop. Stronger aroma than Citra. It has a very funky taste that is extremely definitive, some weird aspect of that sour Southern Hemisphere taste. It is probably the most unique and definitive hop I have used, but I don't like that funky taste. Stone Enjoy By apparently mixes this with Galaxy for a double dry hop. I can totally smell and taste the Nelson Sauvin as I rated Enjoy By a 5.0 for aroma and a 4.5 for taste.
Sorachi Ace - Citrus and spice. Not that strong and the spice is a little weird. A little bitter and grassy as well.
Kent Goldings - Light spice and pine, not very strong, English hops aren't really known for being great dry hops.
Magnum - Light spice and fruit. Not much taste. Another clean bittering hop, doesn't contribute anything particular as a dry hop.
Millenium - Light spice and fruit. Not much taste. Very similar to Magnum, but possibly lighter.
Williamette - Light spice and a little fruit, not strong, more spice than Kent Goldings, not worthwhile for an IPA but could contribute something interesting in a different style of beer.
Polaris - Dank, spice, citrus, fruit. This is a strong taste but the dank and spice overpower and don't mix well with the citrus and fruit. A bit sour as well.
HBC 342 - Fruit, citrus, and spice. A very weird spice taste similar to Sorachi Ace. A little sour as well, although it really isn't that strong as a dry hop.
Apollo - DANK. This hop is as dank as it gets and has a sour taste by itself. When I tried mixing it with other dry hopped beers at the time, it overpowered them. My friend and I did not like this at all, it was so bad we had to dump it, but it might have been good if mixed at 10% as the Heady Topper clone uses ~10% Apollo in their dry hop mix and the taste is not so definitive there. If I hadn't used it successfully in my Heady Topper clone, I would probably rate it worse than Chinook.
Chinook - Spice. This is a definitive spice taste that can mix well with other hops, but by itself it's just a bitter spice taste. Probably the least liked of the C hops, and the most likely hop to give the dreaded cat piss taste.
EDIT: All these reviews are based on dry hopping a beer that had no hops in the boil. While many hops have a similar taste in the boil, even for bittering, some hops that are great as dry hops aren't so great for bittering and vice versa. For instance I can totally taste CTZ if used as a bittering hop, even behind a bunch of strong late addition and dry hops, as in head to head batches other bittering hops gave a much different flavor even though I used the same late addition and dry hop schedule. On the other hand Apollo is a great bittering hop and doesn't give a sour taste at all as a bittering hop, while Polaris does. I also did a SMASH that was FWH with Citra once, and while it wasn't bad, I imagine I would have liked it better if I used CTZ or Apollo for a bittering hop and kept the same Citra late additions.