I don't know anything about the technical aspects between the two versions, and I don't really care. All I care about is what I see with my own eyes. And what I see with my own eyes, as someone who owns both console versions of GTA IV, is that the 360 version looks better. The PS3 version looked muddier. Character faces appeared to use less polys. Sunrises and sunsets looked beautiful and natural on 360. On PS3, it looked like someone sprayed orange juice on everything.
LA Noire looked better to me on 360 as well, but that was back when I had a 2007 Bravia that couldn't do shit with a 720p signal, which is what it ran at on PS3. It would probably look fine on my new Bravia, but I'll probably never know because I loaned out my PS3 copy almost two years ago and don't know if I'll ever get it back.
RDR, never played the PS3 version. I saw enough comparison vids to know I didn't need to bother.