With a crapload of new content added as well.
I've got both, and they're both good systems. I just comes down to what games you want to play.
From the games you've mentioned, I'd say just get a PS3 because you want to play Metal Gear. All the other games you talked about (PoP, Splinter Cell, etc.) are cross-platform anyway. Want RPGs? XBOX would be better, but Valkyria Chronicles should tide you over until stuff like FFXIII and FFvsXIII drop.