Eurogamer has conducted some pretty in-depth tests on the framerates of Grand Theft Auto IV on both the PS3 and Xbox 360.
Overall, they found that the PlayStation 3 averages a few frames per second less than the 360 version, but suffers from no "torn frames". The PS3 average never got about 30 in their tests, but the 360 didn't break 30 by that much.
Of course, my wallet is full of Microsoft's money... so much money!
Check it out over at Eurogamer.