i'm very happy with my go, had a 1000 before.
the go excels at emulation, because it has the superior buttons. it uses miniswitches (clicky ones) which are incredibly responsive. the dpad is certainly the best of any psps. it makes playing anything between nes and gba a pleasure. most ps1 games too, though some 3d games really would rather have an actual ps controllers analogue stick.
having said that, some psp games are kinda hard to play with the gos 'cramped' button setup. mainly those which use both the dpad and the stick to control different things like walking and item management and several button combos like L+circle, R+square, l+r+ triangle and crap like that. those were somewhat uncomfortable even on a bigger psp, but on the go, those are close to unplayable. special mentions go to the metal gear and ff type 0.
those games and generally 3rd person 3d games for the psp like gta, kingdom hearts or crisis core are more comfortable to play on a not go, since the analogue stick is easier to access and also bigger on those.
your decision should definitely be between 3000 or go though. temp custom firmware is not a big deal with sleep mode and even if you power down completely, it literally takes 10 seconds to get back into custom mode. only time this really becomes bothersome at all is if you're trying to setup an emulator/homebrew/rom/iso with a tendency to crash on wrong setups or with the wrong iso driver.
and to be honest, if you have any way to testplay a go for a day or so, you should do before buying one. i'm sure you can get used to a lot, but the go isnt exactly made for huge hands and I've read of a bunch of people who just couldn't get used to the small form ever (they might've been over exaggerating though)