I don't have an XBox yet, but I got the PS3 for the blu-ray capabilities initially. Like another person mentioned, there is also 3D capabilities on some of the games. I think you can also get Vudu (not sure if available on xbox or not), which is a PPV movie service. VUDU has a selection of 3D titles, and hopefully that will be expanded soon.
PS3 doesn't charge (to my knowledge) for online gaming, but I know for a fact that Xbox does.
If you have music/video on your pc, you can also stream them via the PS3... again, not sure if that's possible on Xbox, maybe it is.
Point is -- PS3 is my choice for all its functionality beyond just gaming.