foleyjo said:
If you want to play PSP games as well then get the PSP.
If you just want emulation go for the GP2X (maybe with a cradle) or wait for the Pandora
It will be for emulation only, just want to make the right choice.
Well, the GP2X and Pandora screen resolutions are better for emulation, because most 16-bit and under systems have resolutions around 320x240. The GP2X's resolution is 320x240, and the Pandora's is 800x480 (a multiple of 320x240, plus some more space on the sides). The PSP's screen resolution (480 x 272) doesn't fit very well, and means that either you'll be using a pretty small part of the screen or there'll be some ugly upscaling.
On the other hand, the PSP's PlayStation emulation is much better than the GP2X's (but some other simpler systems aren't emulated so well).
The best handheld for emulation will be the Pandora (good screen, good emulation of systems likely up to the N64), but it will also be the most expensive one.