I read on beyond3d, from people who know more than I could imagine, that the PS3 version in the early screenshots used a color filtering hack to correct the problem with the walls in the beta sometimes looking too blueish but that the hack (at least in the first batch of screenshots) made the sky look green (blue+yellow=green). I guess the 360 beta would have the problem of having waterwalls but I hope they fixed those color issues between the versions. I'm sure it's because of the gamma difference or some shit on the GPUs (which is why the brightness looks different in identical 360/PS3 games) that IW had this problem but it's very minor.
off-topic, but I hate those versus comparisons that gametrailers does where they compare two different games (VF5/DOA4, Resistance/Gears of War, etc.)