I totally agree in many cases,
but im not sure how true it is with an optical switching SSR because different brands seem to run hotter than others, and theres a point of diminishing returns I think .. if you bought everything thats rated for much more the cost ,size increase and ease of use of a device can suffer...(thicher 10g cord is harder to bend and use for example when 12g sjoow is rated for 25a use. or a 50a service is really not going to be practical if you only use 25a of it as many do. even after taking the common advice here to spend more on 50a.
all im saying is if its a decent 25a ssr its meant to handle up to and including 25a without problems.. if cost is the same or its not a factor than yeah id go 40a but its not as big a deal to have and use an appropriately sized 25a one as some like to say it is.