Personally, I'm level 49 in Forza and pretty close to Level 50. It's fun, but there's so many things wrong with Forza.
I posted my huge review:
https://www.gtplanet.net/forum/showpost.php?p=3644577&postcount=100
I mean honestly the game looks pretty poor at native resolution, the only 2 places the cars look good is at the main menu and the rendering before the race starts. This is where the game uses Mesh Streaming. Once you're in the game, it's like a cartoon. Even when browsing cars to buy they look like plastic models kits someone put together.
Have you guys seen this bias comparison video of Forza 3 against GT5 : Prologue?
http://www.youtube.com/watch?v=JQNqU6YW9zI
I had my brother take a look to give me the technical breakdown of the bias comments. The most important ones I'll comment on:
"60 FPS". GT5: Prologue replays run at 30fps, which is what we're watching, not 60FPS which is solid during gameplay.
"Motion Blur". The 'motion blur' mentioned for Forza is actually a low LOD (Level of Detail) texture streamed at long distances rather than awesome motion blur technology, while Gran Turismo uses a higher definition texture at all times compared to Forza. The car not blurring in GT is a case of depth of field not motion blur, where the car is kept is kept in focus and the foreground/background are out of focus. Depth of field is current gen technology unlike motion blur.
"Tire Marks!" or tyre marks. This is just decals, like bullet holes in Counter Strike, nothing special. I suspect GT5: Prologue doesn't have them because, they're looking at a better method of implementing tire marks on the road surfaces.
"Shadows and HDR on tracks". Actually if you want to compare lighting/shadow technology GT5
rologue without a doubt uses better technology. Illuminate Labs is currently one of the leaders in Game Lighting technology with products such as Turtle and Beast. The global illumination technology used with turtle and beast, give products like GT5: Prologue, Mass Effect, Mirror's Edge and Killzone 2 realism beyond anything in Forza 3. The lighting in Forza 3, either uses low definition lightmaps or none at all and lack of high detail normal maps is disturbing, which you can see in their terribly lit rocks walls and flat grass.
"Grass" look at the GT5 side from 4:04 to 4:29. Then look at the flat "green" apparent grass in Forza.