One big problem is some games can't utilize the touch screen features on VitaTV.
I can't imagine the camping in dragon's crown without touch screen, or the lock-on in Senran SV being changed from touch anywhere to dpad, which makes it harder to toggle lock-on and moving at the same time.
Dual shock 4's got that track pad in the middle of the controller. You can use that in SV for all touch stuff, seen it on YT And it look's like it works pretty well. Not sure about Dragon's Crown or any other game as of yet.
Shinovi (which they're working to make compatible in the US FYI) is the main reason I want to pick one of these up at some point. I'm waiting till it goes on sale though, I don't have enough money to spare atm