Depends on what you taste in games are and what controller you are more comfortable with.
With PS3 you get a Blueray player, free online (PSN) and the option to install higher capacity HHDs.
The Xbox 360 uses the HD DVD format which is faster than blueray in terms of reading data of the disc, you are required to get Xbox live gold to do most things like use Youtube or IE which means money, you also need microsft points to buy things although i think microsft might have switched to real money instead, the biggest capacity hard drive you can get is 320GB.
Each consoles also has its own 'exclusive games'.
Like the PS3 has uncharted, killzone, little big planet, gran turismo and the Xbox has halo, forza, fable, you can find a full list of them here - http://en.wikipedia.org/wiki/List_of_video_games_exclusives_(seventh_generation)
And don't listen to fanboys and their claims, its about what you like, not what they like.