What do you guys think?
Here's a comparison from Digital Foundry.
-http://www.eurogamer.net/articles/digitalfoundry-tech-analysis-forza-motorsport-4?page=3
Most of it's just an in depth look of F4 but at the end they have a comparison bit between F4 and GT5.
Pretty much the same thing that lens of truth said. They both have their strengths and they are both admirable sim racing games.
"The comparison is intriguing on a number of levels: it demonstrates that the aesthetic look of the two games is very, very different - especially in terms of the lighting, and that while Forza's performance level is wholly consistent at 60FPS, GT5 can drop frames and tear, even at 720p (with further frame-rate drops if running in 1080p or 3D modes). Also remarkable is how completely different the audio scheme is between the two games. On these courses at least, there's a pretty strong argument that Forza has considerably more track detail, but you can make up your own mind with this Forza 4/GT5 comparison gallery."
"The overall impression we get from playing both games back-to-back is that each has its own strengths: in terms of the handling and audio Turn 10 could well have moved ahead of its competition while Polyphony's minute attention to detail (to the point of implementing working headlights/dynamic shadows in the cockpit view) plus the sheer range of different driving scenarios remains second to none. Both titles excel in their own ways - especially in terms of visuals - and we have the feeling that motorsport fans probably own both consoles and are equally invested in both games. We aim to take a look at how these games play with a number of different steering wheel peripherals in a future Digital Foundry hardware article."
I think the sound in Forza 4 sounds better than GT5 and the outside environments are much better than GT5, but GT5's cockpit looks better than Forza 4's.
Too bad they couldn't have done an outside car view.