I have never played the XBox version, but have read quite a bit about it on the SH boards I frequent (SH Heaven, SHF, and the old Dark-Legacy)
That being said, content-wise SH2 PS2 GH is identical to to SH2:RD XB. The differences being the overall resolution of the game, since XBox has better anti-aliasing and sharper graphics. I have heard of some complaints about the XBox controls, not surprising given that the SH team is Sony-centric -- but this could be a personal choice issue as well.
If u have both consoles, I am sure both versions will fill your needs. For graphics go XBox, for controls go PS2.
SH2 is really one of the highlights of the series, and may edge up to SH1 as one of my faves. SH2's story is far deeper, more layered, and more twisted that any other SH, and is a damn fine game.
SH1 is the scariest, but as a PS1 game is the most dated
SH2 is the most facinating and has the most mature story development
SH3 is the most emotional, tying back into SH1, and has the most technical polish
SH4 I must confess I have yet to play
I webmaster
http://www.translatedmemories.com/ -- which translates the Japanese "Silent Hill Book of Lost Memories." If u like spoilers, feel free to dig around -- but frankly, I suggest u avoid it until u can at least finish SH2.