As usual, Eurogamer has that question pretty well covered with 100+ comparison shots, a video, and analysis:
http://www.eurogamer.net/articles/digit…auto-5-face-off
Their overall summary:
It's apparent that the PS3 version has an undeniable advantage in one area: even to the naked eye, ground textures on 360 are blurred as a result of what appears to be unoptimised asset streaming. Glitch or not, this basically amounts to concrete and grass textures appearing fuzzier beneath the feet of Trevor, Michael or Franklin, while the PS3 version's remain crystal clear. The 360 does command a minor advantage in frame-rate during synchronised play, but for shoot-outs and high-speed hurtles down the city streets, the PS3 can sometimes pull ahead in these metrics - though the difference is rarely perceptible either way. Since all else is identical across the board, the PS3 version is recommended on the grounds of image quality if you have the option.
Other highlights:
With most late-generation Face-Offs, the best way to put differences into context is to start with the assumption that everything is otherwise the same. For Grand Theft Auto 5 this is very much the case - and overlooking some nitpicks, just about every single geometric detail and effect across Los Santos is like-for-like between PS3 and 360. However, there is one glaring contrast throughout our tests that can't be ignored.
[...]
Despite each console's mandatory installs - 7.8GB for 360 via a separate disc and 8.4GB on PS3 - it quickly becomes clear that there's an asset-streaming issue on Microsoft's platform. This essentially manifests as blurrier textures in a number of spots, particularly for ground assets like concrete, grass and dirt. Whether you're at the city centre or in the wilderness, ground assets beneath Trevor, Michael or Franklin's feet are a pixel-perfect match for the PS3 version equivalent, but the quality dips off noticeably a metre ahead in the player's field of view on 360.
[...]
Running straight from disc, then, there's little to distinguish the PS3 and 360 releases when it comes to object detail, but there are some curious catches. Flying the Cuban 800 plane around shows up variations in grass placement, but more striking is the presentation of palm trees regularly sighted around the city. Their more flourishing look on 360 is unusual given the parity elsewhere, though we notice the upshot of this is a nasty pixel-crawl across their tops during slow pans, suggesting alpha-to-coverage dithering in concert with the post-AA producing the unwanted effect. Also falling within nitpick territory is a slight difference to reflection map resolution while in front of Franklin's bedroom mirror - the PS3 delivering a lower-quality, pixellated alternative to the 360's reflections.
[...]
The target this time is 30fps for both platforms, and it holds at that point for most areas. Overall the PS3 puts out the lower frame-rate for synchronised in-engine cut-scenes, typically by a matter of two frames-per-second and rarely much more. Curiously, the 360 version is the only one of the two to drive upwards from the 30fps target on occasion - far from being ideal, this produces a judder effect due to the frame-rate no longer operating as a multiple of the 60Hz output signal. Regardless, the readings for both consoles stick together like glue during dips below the line, with each going as low as 20fps.
