Thank you for posting this. Everyone raves about the physics in iRacing, so I gave it a try. Played it for several months. And since I track a Miata too, I spent most of my time in the Spec Miata races. After three months of frustration with the awful physics (compared to driving on ice), I came back to GT5. GT5 is not perfect. But where it has faults, it also has strengths. And the strength of the GT5 physics model is that it is far more conducive to racing, or put another way, the racing was more fun.
Keep in mind that iRacing started off as a Nascar sim. From what I'm told, the physics of those cars is pretty spot on. And I would not argue that. However, having been on the track in a Miata, give me GT for the win. Again, for those that love iRacing, I'm not saying that GT is better. I'm just saying that for the one car that I have personal experience with ... I prefer GT. YMMV.
MX