The PlayStation Vita version of Power Smash 4 has some Vita-specific features not found in the PS3 version. Here's some of what you'll find in the game's VT Apps mode.
A first person mode that uses the system's motion controls.
Use the system's multi touch capabilities for a two player match on a single Vita.
Take a picture of yourself with a pro tennis player, and apply filters. You can save the pics if you have a separate Memory Card.
A mini game where you use motion controls to control the tilt of a ship in the back court. Your goal is to strike all the targets on the ship.