I've played this game a lot, both with my Vita and PSTV. While i've found it a lot easier to nail the rhythm of each song on Vita(no input lag) it's difficult to get a firm grasp on the Vita and i've had slip out of my hands a few times while playing a song.

I'm curious how the game would play if one were to plug a fighting game/arcade stick into the PSTV. Would the larger buttons make it easier to hit each note with precise timing?

It might help, but I think the input lag alone makes it a pain regardless of what you're using. I wonder if there's a hack where you could blue tooth a PS4 controller to a Vita?

I think it would be frustrating trying to hit the quicker left-side inputs accurately using a joystick. Like if you're going to use PSTV I think you'd be much better off just using a Dualshock or something but input lag is the number-one killer of rhythm games. There are no good answers.