What you heard is called a rumour. Tekken 6 may well end up on 360. As of now we don't know.
I'd say 360 fans are deprived of top-tier fighters having only Dead or Alive but they just got Virtua Fighter 5 for the PS3 so they have one top fighter now at least.
DoA4 has a lot of depth.
Not VF depth, but it's not the button masher that people who haven't played it properly call it.

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R and SoulCalibur 3 (a little KOF and Hokuto no Shinken on the side) and both games are huge draws during tourneys. As far as balancing goes, it all depends on the players. If the jerk is a 'Scrubber' or Scrub which is what we call a guy who uses the same ****ty cheap move to win the fight, then yeah, the imbalances are pretty obvious. But a pro, a real expert in the game develops his own unique style with whichever character he plays. That's the beauty of fighting games, there's no one way to play a character. There's a plethora of ways to kick ass and look great doing it...that is if you play to have fun and NOT play to win. Definitions of fun differs too. Some people think fun is all about winning. Other feel that is pretty fun dissing other people and whatever they like. Opinions. Like a-holes.