well 1st thing is 1st. The cost.
xbox (250)+ XBL(50) + (you might need it or not, for me i would) wireless adapter (90)= 390
Ps3 (400) +................= 400
A lot of people say that the xbox is a lot less money, but for some ppl like me, they are about the same.
Games
Xbox-- Halo, Gears of War, Bioshock
Ps3-- MGs4, Little Big Planet, Killzone 2
Online
They are both pretty much the same thing except for minor things.
For Example, in COD waw for the xbox you can see the leaderboards for specific game modes, for the ps3 you can't. IMO $50 is'nt worth those minor diffrences
Movies and Songs
The Ps3 has a built in Blue Ray and you can get free songs easily in only a matter of minutes. You can even play songs while in game for certain games like Killzone2.
The xbox im not completely sure, but i think the ps3 wins in this category.
So IMO the ps3 is better, well for me at least. I know some will disagree and fight over what i just said, but those are the facts.
MOst people use the regular ethernet cable to there 360... so that means you can subtract the $90-100 it costs for an wireless adapter. If you need an ethernet cable....theres this place called wal-mart that sells them for under 20 lol. The 360 is better suited for online gameplay.