I worked at Sony for two years and quit 3 months ago (from when I was 18 ti'll 20) and I was one of the persons to test, play, and compaire the PS3's that were produced, and check for bugs.
Getting to the point ->
One day, I was doing a side-by-side comparison of Need For Speed: Carbon on the same tv using picture-picture and I found noticable differences on both systems.
For example, the PS3's had more details, but the Xbox 360's had more glossy, shinner graphics (I.E., the lights shinned bright and you could not see as much texture to the gravel, dirt, etc.)
Another thing I noticed when In a race (stand still at the starting line) was that the PS3 was actually missing some of the details on the road, the reflections, and some monuments In the background.
And one more thing I researched on. It might be surprising, but this Is Indeed true, and which I stated previously, Go with the 360.
When we broke down parts of both systems, and read the labels and so forth, a team of our employees came to the concluison that If you wanted to run an Xbox 360 game on a PS3, you would have to dumb-down the game before you could even try to run It.
That and, When setting up Xbox's Live feature, It only takes a few cables and you're done. While the PS3 want's your ISP, your IP address, your tellephone, email, etc. It's alot of work for no reason.