There are a lot of theories out there and I think one of the most corrupt of them all is that spunding creates finer bubbles than force carbonation but I think it's incorrectly attributed. If you were to split the same beer into two cold side processes, you'd likely find that the spunded "fine bubble" beer simply has a slightly higher carbonation level because the forced carbonation version, which may have been carbed through a stone in a brite tank just didn't reach full equilibrium.
The other thing that produces fine bubbles is lack of nucleation points in the beer. That is, a beer that is brilliantly clear will crack co2 out of solution and that tiny bubble rises and forms the head. In a hazy beer or one with fine particulates, those particles can be the source for a few Co2 bubbles that happens at the same time and the bubbles combine before they even rise up through the beer. Big bubbles.
So, lagering or fining, is the answer in my opinion.