As an exclusive, it would have perhaps performed better. Cosmetically, it most certainly could have performed better. Tekken has never been released on 2 separate platforms before, so I guess that may have hurt it a bit. IMO though, it was how long it took the game to finally release that may have hurt it, which also would not have a been a problem, or as much of a problem, had it been released on just one platform.
Regardless, it's all speculation, and irrelevant at that. The game is here now, it's not a bad experience by any means, and I think people should go buy it and enjoy no matter what platform they choose to play it on, if they can afford to and are Tekken fans.