Ya but the game has to load each cutscene and mission, that's where the PS3 should be faster, at least as far as I've read.
I have both consoles and I think there is a FEW seconds faster loading on the PS3 but I haven't checked with a stop watch
I've already played through the 360 version (only the story so not 100%) cause I got it first for the 360 but I'm on my second play through, now on the PS3 (I need to kill some different people this time!).
The one I like best is the PS3 version because I like the controller better, it is a bit brighter (yeah I know you can fix it in the options but it is not the same anyway) and the colors are a bit warmer.
Not sure how to explain it but I'll try: The water color effect seems to start a bit farther away on the PS3 but it seems like the PS3 fades it more in some way. Not sure if it made any sense.
There is also a less aliasing (NOT much) on the 360 version but it seems to load buildings and other "distant" stuff a bit slower and you can see that when driving really fast.
Another thing I noticed is that the sound is a bit clearer on the PS3 version. I can hear more background stuff, but this might be because of the console since it is more quiet. The guns sounds a bit different too but I don't know if it is better or anything, it's just different.
There are noticeable differences but I don't think you'll see them right away, and remember that I played about 40 hours on the 360 before I fired up my PS3.
There is absolutely no point in buying this game on a particular console because of differences between versions.
The game is one of the best I've ever played. I feel like it is more grown up than the others and the story/characters is more believable than before.
Using HDMI on both (digital sound too) in case anybody wonders.