Dundon's
W.G.P
I've a PS3 and that's what I'd go for if you got the money. If it's only to play one or two games, then the Xbox is cheaper and a decent online experience.
However, PS3 games are much more fluid and have a better feel. Also, the Blu-Ray aspect of it helps, meaning that soon games will be massive on the PS3 (as Blu-Ray will be able to hold up to 25 times the data a DVD can).
In conclusion - for a cheap thrill, get the Xbox. For a long term and reliable girlfriend, choose the PS3.
Ta luv I'll take it all on board before making my decision.