Q: There’s like 5 different platforms for CvS2. Are there any differences?
A: For obvious reasons, everything will be compared to the arcade version of the game.
Dreamcast: For all intents and purposes, arcade perfect. There have been some complaints about speed differences between the arcade and DC versions, but it’s an established fact that there IS no standard arcade speed. Different arcade cabinets all set on the default speed of 3 will have slight (sometimes major) speed differences for no apparent reason.
PlayStation 2: Pretty much identical to the DC version (and therefore, identical to the arcade), the PS2 version does sport slightly higher resolution. Nothing game-affecting, though.
EDIT: Yun has a really random game-crashing glitch: hit the opponent with a You Hou super, then immediately do the qcb+P palm move after. Game crashes for no apparent reason.
X-Box: Lots of differences here.
* EO Mode: The Easy Operation Mode lets players do special moves and supers at the touch of a single button. Obviously aimed at beginners and mashers.
* System: RCs are completely removed. Not sure if other glitches (OTG grab CCs, tech throw glitch, etc) were removed.
Grooves: S-Groove reportedly charges its gauge faster. P-Groove gets the (amazingly broken) ability to do super cancels. A-Groove can jump and whiff an air attack and still activate CC afterwards. They can also cancel most connected air attacks into CC as well.
* Characters: Sagat, Blanka and Cammy all get a 5% damage reduction across the board. Certain characters I can't remember got a 5% damage boost, I think it was something like Dan, King, Kyosuke, Maki, Eagle, Gief, Yuri, and I think Zangief...? On a more specific level, the only real tweaks found were that A-Maki can no longer juggle a CC after her punch throw in the corner, the Kim infinite doesn't work and Cammy bounces a lot higher on a blocked DP. Hibiki still can juggle a CC off of her kick throw for whatever reason though.
And… that’s all I can remember at the moment. There are certain false rumors being spread around by XBox lovers, like the top tier characters’ moves having less priority and Sak/Bison’s CCs doing less damage. Don’t believe them.
Gamecube: I don’t know exactly for sure, but it should be exactly the same as the XBox version. I’ve heard random rumors about stuff like Sagat not being able to buffer supers off of his low fierce, haven’t had a chance to check them though. EDIT: this has been confirmed to be true.