PS3: Convince me.

[Typhoid]

The PS3 is a delicious system. First of all, Valkyria is a fun game. I still haven't beaten it because I have a gajillion other things I'm in the middle of.
Secondly, the slims are 120 gigs. 120. 1-2-0. That is worth it alone for the price they're selling for.
The backwards compatability doesn't bug me. I still hook up my PS2 when I want to play a game from it. And 360 doesn't have it either, so it's really a moot point.
And it DOES play blu ray - and it does it very very well.
The slim also got rid of the problem where the speakers would hum on a TV without hi-def if you're playing a normal DVD. It works perfectly now.
No batteries for the controllers is a gigantic plus.
It's tiny, light - and silent.

As for games coming out - there isn't much that isn't out for the 360. Which is why it comes down to preference. Granted, Sony won't fuck your ass dry (then again you're into that thing) with online charges to play their games - which is a giant bonus if you play online games.

Personally, I haven't ever played a Ratchet and Clank game, but I hear nothing but good things from them.

I would say this though - don't save the money up for Diablo 3. Spend your money now.

Edited for rampant spelling errors.