Tournament standard is PS3 (if this changes in the future then disregard the rest of this post), even though you'll come across an Xbox every now and then. Civil War was an Evo-qualifier that was all Xbox 360, but that was because of the host who had like 30 CRT's and he had no choice if he wanted to get it done in a weekend. Soul Calibur 2 on PS2 and Marvel 3 on PS3 have been known to have slowdown issues, but even those still got played on Playstation consoles. There has to be a much bigger technical reason not to run a game on a particular system other than stage-specific slowdown or some minor graphical difference.
If you guys want DoA5 to mesh well with the other major fighters at events like Evo, then you may have to play on PS3. If that happens, don't use the "but we've played on Xbox since 2001" defense or else you'll just look like whiners from a community that's been cut-off for years. If you want your game to get big and be a part of all the other titles, then adapt or die. Don't be tight-asses about it when you know people have enough trouble as it is opening up to the DoA community because of how people feel about the game. Don't look at it as "giving in," look at it as "supporting" or "starting anew" for the sake of the game's longevity. And if you don't even go to offline tournaments then nobody cares what you think in this thread. The fuck up.
Lastly, don't mention shit like MLG or events like it (where fighting games go to die) to support your reasons. People hate those tournaments as far as fighting games are concerned, except the people getting payout.