It all depends on your firmware. I'm on 3.63 with no henkaku so I just use Ark. so now I'm able to play a bunch of my favorite games from psp on my vita that were never digitally released (I'm talking about you final fantasy VII crisis core) and even better I can play the undub of all of them as well!! So ark was a plus for me. It also runs a bunch of emulators too but I only have gpsp as the n64 emulator for vita is garbage...but the gpsp emulator is kick ass. It works with almost all the games I believe. I even patched up a few copies of Megaman Battle Network with the WiiU ips patches to add the secret chips and BAM! They all work.
But again..it all depends on your firmware