Let's get technical for a minute and also get the technical assessment from pros.
PGR4 = 1280x720p @30fps 2xAA, 6 cars, 100K average polys per car, no HDR lighting
GT5P = 1280x1080 @60fps, 2xAA, 16 cars, 200K average polys per car, HDR lighting, ray-traced garage area @1920x1080p
It's not even close.
"So the game runs at 1080p, 60 frames per second. That's something that, even on PS3, a lot of games haven't been able to accomplish. How much of a development concern was that when you were building it? How much time did it take to get the engine – which looks great running at that resolution – up to snuff?
First of all, Kazunori insists that a racing game runs at 60 frames per second. That's a must have from his point-of-view. And the characteristics of racing, or racing games, is that you're most of the time driving at high speeds. At high speeds, your view points are in the distance. You need detail, even for distant images, and 1080p was the only resolution that he could possibly think of. Both 60fps and 1080p were both must haves for the GT experience to be the GT experience. They've done some experiments on 720p to see if they could find a compromise but the minute they saw it, it was out the door."
http://www.joystiq.com/2007/10/24/joystiq-interviews-polyphony-digitals-kazunori-yamauchi/
