Ignoring factors unrelated to the game itself (Live vs PSN, size of respective communities, tournament usage, etc.), are there any known differences between the two versions? That actually would be nice to know.
Depends on the game. I find better comp for BlazBlue on PS3 but better comp for SSF4 on Xbox. PS3 I usually run into worse connections because of all the people who use WiFi but Xbox tends to have more rage quitters like you said (all that rage practice from Halo). Xbox definitely has more people online I think.
As far as the actual game performance, all I know is that Xbox can upscale the 720p game to 1080 by itself while the PS3 relies on the game software and your TV. Usually Xbox wins but since this game isn’t exactly GT5 you probably won’t notice much unless you have a huge TV (50+).
Best suggestion would be to find out what your local comp uses since that’s the best way to get better. Some areas just happen to use a certain system more often. If you want to compete and go Xbox, you’re going to need a dual mod stick or two sticks since the majors use PS3.
I wish MadCatz would stop fishing for worthless system logos and just make and sell a dual mod stick.