All I can say is try all three versions before you buy your copy (well, that statement varies depending in which consoles do you own)
I was very excited about Heihachi being in this game, but when I actually played it and saw him in there, I wasn't impressed at all, it was just the same old Heihachi with exagerated moves. (I'm not saying he wasn't cool, he just did not impress me at all) But then I played the GameCube version and... Link was so awsome... they did a great job with him. Also, the loading times in GC are much faster than in PS2. Now I still haven' played the X Box version but I've heard that Spawn is awsome.
If you don't care about the "exclusive" character I recommend the GC version over the PS2 one, since teh grahpics are somewhat nicer and the loading time is much faster. And the GC controller worked PERFECTLY in this game, it wasn't a problem at all to fight with it.
Thanks for the review Meryl-chan.