I'd go for the emulator for the PSP, if by emulator you are talking about a handheld emulator, because the games are meant to be played on a handheld, and if it is an emulator you don't have to actually have copies of games, you just have to find ROMs for the games. For any console PS2 or older i'd go for the emulator because the emulator is always better because of the ease to getting games, unless you are planning on using a raspberry pi. If you are using a raspberry pi, it might have a bit of trouble emulating PS2 games, so I'd stick with PS1 and older.