Some of the guys on gaf raised an interesting point. It looks as if the GUI is 720p on both sets of screenshots, implying that the 360 shots are accurate. If they were simply captured at a lower resolution and then upscaled or something, this would have also affected the menu overlays and subtitles.
Also, if you look at the two shots of the dark haired girl, it looks as if the ps3 version has more light sources. Look at the lighting on her midrift and right arm.