The PS3 "mortgage your house" GPU is underpowered and might get half the number of polygons on screen compared to the XBOX 360 "takes it from behind."
This article talks about the issue.
And this article backs it up.
"You end up with a console with half the triangle setup rate of the 360, a crippled CPU that is a bitch to program, and tools that are atrocious compared to the 360. To make matters worse, you have an arrogant set of execs telling us that twice the price is worth it for half the power, a year late. If it isn't already too late, Sony had better do something about this recto-cranial inversion or it may very well sink the console."
My take on the whole issue? The XBOX 360 came out ahead of Sony's predictions, and the PS3 is suffering for not having as much time for it to be developed and tested as Sony wanted - and needed.