It's bad enough that for years they've been porting arcade fighters to home consoles without doing anything to the control scheme, now they bring that same thoughtlessness to the Vita and the results are horrible.
Trying to play Street Fighter X Tekken on the Vita is awkward at best. It's near impossible to get a firm handle on all the moves considering you have to press the left trigger for a heavy kick. They offer alternative control schemes, none of which were well thought out, and all of which undermine what a fighting game should be about: timing and combos.
Bottom line is the Street Fighter series, with it's six button attack and QCF movements, have never translated well to the dual shock. So I'm just not sure why anyone thought they would translate to the Vita. It's a shame too, because there certainly was an opportunity here to get it right.