We just got both versions here at work and did a/b comparisons on an lcd tv. Lighting seems more or less similar on both, but the resolution difference is glaringly obvious. the PS3 version is clearly running at a lower resolution. We looked at similar locations back to back and the stair stepping on the PS3 version is much worse, so much so that I couldn't help but notice it everywhere. I seriously doubt the PS3 version is running at 720p, it appears to be significantly less. Anyways, I'm glad I did the comparison myself instead of trusting the magazine reviews. After seeing both in action its a no brainer to me, getting the 360 version today.
Could you do me a favor and try disabling any 1080 (i or p) mode on the PS3 and let me know if the situation improves. Seems a few people reported even worse aliasing with these enabled.
Thanks