The PlayStation Vita version of Marvel vs Capcom 3 will allow you to control the PS3 version using the Vita as a controller.
According to Andriasang, those who own the PS Vita version will gain access to this unique function, allowing you to use the optional touch controls for controlling the action. Apparently you can even customise the touch panel with four of your favorite moves.
As well as being able to control your character, the Vita also allows you to control replays of your matches, meaning you can play back your matches, pause, forward, show button presses, and even surround your characters in hit boxes.
This sounds fantastic and if other games take advantage of the same sort of functions, then the PS3, along with the Vita is already eating into the unique selling point of the Wii U.