Depends what you are really looking for. The PS3 is a technical marvel and a very competent home media system. With the PS3 you have Blu-ray as standard and shortly Sony will be releasing it's competitor to XBL called Home. The gaming side is a bit lacking at the moment, hopefully that will sort itself in the next 12 months.
The 360 has a better current online service imo and a much better selection of games right now. Although if you plan on playing HD movies then you'll have to buy an add-on with the 360, unless you already have a standalone HD player. Personally if you are a gamer I would go with a 360 right now.