I think both games look terrific.  But there is something in GT that makes me like it more than Forza.

Although the graphics aren't that huge a leap over any other games of the same kind (even though it does achieve a lot of things on a technical point of view that other racers don't, even if they're not necessarily notceable right away to the naked eye) , the way it mimics reality with accurate colors, intricate lighting, the sheer beauty and accuracy of its cars, the way the game feels very sober, very "gentleman focused" (for lack of a better "expression".  There is definitely a unique feel to that series that I really enjoy) are all things that make me go back to the series.

Forza 3 have really good graphics as well, but the game feels more arcadey, and the graphics don't look as realistic to me.  Mostly because the team behind the game relied a bit too much on vivid colors and they overdid the texture work a bit.  The landscape sometimes reminds me more of Daytona USA than a game supposed to be a sim (just look at those rocky palissades in some of the race tracks to see what I mean). And the lighting certainly isn't as intricate as the one found in GT.  Performance wise, it runs flawlessly, butter smooth as they say, and the game does look awesome in the end. 

Maybe I'm just more used to the GT feel, which makes me seek it insimilar games.

I'm only talking about the look and feel of the games here.  As far as gameplay goes, I haven't spent enough time with Forza 3 to form a definitive opinion of it. 

Because said "real driving simulator" isn't attempting to simulate realistic crashes.  It's trying, and succeeding to simulate real car handling and behavior for over 1000 cars, among other things.

Car damage is just a plus, and they might perfect it with upcoming titles.  But that has never been the point of GT.

So driving into rails via sharp turns to win races  without any con is part of being a "real driving simulator?" Part of being a simulator is knowing you can simulate a cars behaviour and face the consequences,This involves learning from mistakes via damage to your car.  Yes you're not trying to crash your car willingly but knowing you can instills the fear to make you drive even better. Leveling up to unlock damage, something that should be in from the get go is a joke.Atleast increase  damage penalities for every level gained.

A much better article by Digital Foundry, the wizards at Eurogamer:

http://www.eurogamer.net/articles/digitalfoundry-gran-turismo-5-tech-analysis

"That said, achieving 4x MSAA with frame-rates and details as high as this is indeed a technical achievement unmatched by any of Polyphony's competitors (Forza 3 is 720p with 2x MSAA, for example), and there is a definite feeling that Kazunori Yamauchi's team likes to push boundaries like this."

For a game that's been in 5 year dev time VS 2 years for Forza 3, is on a more powerful machine, with more experienced devs behind it, you would hope so!

Before Forza 3 there was Froza 2 and before GT5 there was GT5P so it's a little misleading saying Froza 3 was 2 years in development when forza 2 was a stepping stone.