Gamereactor have picture comparison with Tekken 6 Playstation 3 vs Tekken 6 Xbox 360 (preview versions). Use the link below and click "Större bild" to get the full resolution. Both versions are supposed to be really good, actually.
http://www.gamereactor.se/nyheter/19321/Tekken+6+eller+Tekken+6%3F/
http://www.gamereactor.se/nyheter/19321/Tekken+6+eller+Tekken+6%3F/