So, you love Ultimate Marvel vs Capcom 3 - so much that you've bought the game on both Vita and PS3. The next logical step is to play both at once, by using the former to control the latter.
As reported by andriasang, the Vita version of Capcom's superhero brawler will include a few unexpected cross-platform features. By using the Vita as a controller, you'll be able to play the PS3 code with the benefit of the portable's on-screen touch controls, which look to work in much the same way as the 3DS edition of Super Street Fighter IV.
While that may not particularly appeal to hardcore players, they may appreciate the other cross-platform trick: you can use the Vita to show replays of your matches, with the option to show hit boxes and button inputs.
It's a nice trick, but I can't imagine many people will buy both copies of the game - and of those gamers, how many will want to use the Vita as a controller?
The replay functionality is nice but again, iId bet most people would prefer to look at their performance on the main console.