sudomod

I want to build a modified game boy classic that can play game boy, game boy color, go advanced, nes and snes games, but looking around I've also seen a lot of pigrrls and other builds. Is there a difference in what they can do? While I'm asking, is the pi zero preferred over pi 3 for these kinds of builds?

Pigrrl is a whole different unit from what I know, gameboy zero uses the gameboy shell.
Pi3 is good for some of the more involved games, but everything I've tried in the systems you mentioned, the zero is fine.