I have both and much prefer using UAE4ALL. Mostly because the psp screen has terrible motion blur when running 2D games. Both emulators are very comparable in speed despite the gp2x having a slower processor it is from a completely different architecture so megahertz to megahertz comparisons dont stand up. Also UAE4ALL now uses the cyclone arm asm 68k core. Many features have been stripped from UAE4ALL such as savestates and extra memory support so that helps speed it up also. the gp2x also has UAE2X which is based on e-uae but that requires more work before it is as useable as UAE4ALL or PSPUAE.
