Personally, I'd go for the PSP. Easier to play on and it has the bigger screen. And, based on experience, the second screen really throws me off when I play GB/GBC/GBA games on a DS.
Hmm... I've been thinking about that, but I wasn't really sure about it... Can you configure the controls for GBC/GB games? I have a few rhythm games where the start button has a manditory use and needs to be set in a place I can quickly use it at.... And some GBC DDR games that I'd like to have the two unused buttons set as arrows. XD If I can't reconfigure some buttons, I may just keep my GBC usage to my DS. And meh, I have a 3in1... If the compatibility of GBA on PSP doesn't cover the games I want, I'll just play the games on my DS...
Compatibility of the GBA on the PSP is nearly 100%. The only issues I've seen are the opening FMV of Kingdom Hearts Chain of Memories freezing/slowdown and needing to be bypasses (runs perfectly after that). I think GBA on the NDS (without an expansion pack) is still not perfect. With an Expansion Pack, the DS (not DSi/XL) has GBA system hardware and can run games just fine, because it's not emulation. SNES on the DS has issues with some of the more popular games because those games had some graphics processing done on the game cart rather than the SNES. I believe the PSP SNES emulators run these better than the DS SNES emulators do. I played Mario RPG on my PSP with a little slowdown during high-movement times. My PSP is a 1000, I don't know if the 2000s work better with their higher RAM.
Honestly, there isn't much difference in the 2000 version of the PSP SNES brew. But it was recently updated so it fixes most of the issues it had.
Yeah, I know. I hate SNES emulation on the DS mainly because it doesn't cover the games I want to play. And right now, the only game I can get running perfect at near-full speed is Seiken Densetsu 3... I'm still looking for a PSP SNES emulator that can run Kirby's Dream Land 3 at a reasonable speed... And Tales of Phantasia didn't run at a reasonable speed either. My PSP is a 1000 too. XD On the DS, I couldn't configure the buttons of Lameboy just the way I wanted... I was stuck with premade button layouts. Speaking of GBC/GB emulators, how's the compatibility on that emulator for the PSP? There were a few games on Lameboy that I couldn't get working correctly (some didn't have sound, even with sound enabled and turned up all the way)