Choosing a PSP: How many full games are available for download for the GO?

I want to buy a PSP but I don't know whether to buy a Go or a 3000.

I need to know if the whole catalogue or at least all Square Enix games are available for download in the PSN before I choose any of them. Also I want to know whether I can also play downloaded games on the PSP. Could you give me some advice? Thanks a lot

Well I can tell you that not all SE games are available for digital download. Kingdom Hearts: BBS was specifically released as UMD only.

You can play downloaded games on a regular PSP. Provided you have a large enough Memory Stick.

I suppose it should also be mentioned that if you want to play PSP games on its upcoming successor (NGP/PSP2), they will need to be digital copies. The system won't have a UMD drive.