well since its from the devs who made netkar I think we can say it has the most realistic tyre model and a very realistic driving physic you can get as a consumer for entertaiment (game)
they also really polished the graphics of the game which is a big plus compared to netkar.
Also tracks are laser scanned which should make them (nearly) as accurate as iracing.
but iracing still having the better online play.
I really hope they can deliver and put pressure on iracing.
I'm not extending my iracing subscription for this year and spend the money on ac instead. That shows how good it really is.
edit:
if you compare sales wise then yeah no way it can compete.
if you say realism and graphics then ac already won.
if you ment numbers of cars/tracks then gt won.
if you compare the whole game without sales its hard to say since its not completed.
