About.com has three articles with reasons why you should either by a PS3, a Xbox 360 or a Wii.
http://playstation.about.com/od/ps3/a/5ReasonsPS3.htmhttp://xbox.about.com/od/buyersguide/a/5reasons360.htmhttp://nintendo.about.com/od/toppicks/a/5reasonswii.htmComparing the reasons to by a Xbox 360 to a PS3 is revealing.
#1 - You Won't Find Better Games
These "better games" are Halo, Rare's library and a few old Valve games.
I do agree that I miss Rare's games, but it's not worth choosing another console over, unless you're a near-stalker fan of the company (they had awesome games for the Nintendo 64).
On the Valve games, everyone knows those are shitty ports, the CEO of Valve even admitted it several times. Valve makes games for PC and Mac first, and then ports them to consoles. And, Valve will begin porting their newest games such as Portal 2 to the PS3, starting this year.
Basically, this whole argument is stupid. Every console has exclusive games.
#2 - You Can Play Friends Online and Download Demos
And you can also do that on the PS3 or Wii. For free, while it costs € 5 a month on the Xbox 360.
#3 - Its 'Achievements' Will Keep You Motivated
The PS3 has trophies, but it's basically the same thing. Next.
#4 - The Xbox Streams Videos and Music
All features mentioned here, the PS3 can do them too. Even more, because the Xbox 360 only plays WMV's, while the PS3 can play DivX out of the box. The PS3 also has VidZone, which lets you watch videoclips all day for free. Beats the crap out of MTV, and Microsoft's RROD'ing console.
#5 - Parents Can Control What Their Kids Do
*yawn*, so can every other console.
Summing up the article, the only reason to choose a Xbox 360 over the PS3 is to play Halo.