Anyone? I know the Game Kiddy 350H has a faster CPU (but way less RAM) but that's closed source, correct?
The GK350H has a faster CPU (1.5GHz Ingenic X1830 vs the 1 GHZ JZ4770 mips in the RG350) which would make PSX emulation much better. Some titles that were previously unplayable or only playable respectably with frame-skip enabled would probably run much better. Bloody Roar II, for example. The latest CFWs for the RG350 and updates to the PSX emulator by gameblabla have helped tremendously.
I'm not sure how relevant it is, but the GK350H only has 128MB of RAM where the the RG350 has 512MB. That might not be a factor as I don't think emulation is memory intensive.
The real delineation comes from the button inputs. The GK350H is missing the right thumb-stick and the L2 and R2 buttons for a complete button layout. The RG350 has all the necessary buttons. The up-coming Pocket Go 2 also suffers from not enough buttons for proper input. I've heard there are workarounds for this, but I'd much rather have the proper button inputs.
For me, the RG350 is the better unit because of the included button inputs, but most of the PSX titles I play are RPGs and not really that intensive to emulate.