Personal preference. If you have lots of Windows enabled products, you can connect them to the XBOX. But if you have Sony products or enjoy Blu-Ray movies, then go for that.http://en.wikipedia.org/wiki/Category:Xbox_360-only_gameshttp://en.wikipedia.org/wiki/Category:QPlayStation_3-only_games
(copy & paste above link into url and remove the Q - stupid forum software doesn't have a no-parse option).
I wouldn't hold my breath for Valve's console; Newell will throw money at it to make it work, but MS and Sony have the experience and won't want to lose ground. In other words, they'll make sure their next consoles are amazing - and with Oculus Rift coming out, they will be.
EDIT: tried fixing the screwed up link, spelling mistakes corrected