Saw this very interesting blog. Basically this guy took all the main sites that do console "head to head" (IGN, Eurogamer, and Lens of Truth) comparisons, to see what he could find out for overall trends. Although he could have used clearer graphics and made things a bit simpler to understand imo, still a worth attempt.

http://misterslimm.wordpress.com/360-vs-ps3/xbox-360-vs-ps3-head-to-head-face-off-results/

There is much more info at the link, I just posted a screencap of the summary!

Edit: hmm, at the time I posted it I thought this was a fresh article, but now it looks like it may be a bit  old...I'm not sure, hope not.

I will never understand why people make such a big issue out of things like these, Just enjoy the games!

Most of these could go either way with only a very small differences. For example in one comparison Ps3 had the higher frame rate yet this causes a little more tearing than 360. In most case (i have both systems) I can't tell any difference visual without putting both of them side by side. More often your HDTV/monitor  make a bigger difference visually than which system you play the game on.