Dunno about the handling. Haven't played either for very long. Project Cars was the most realistic to me, once you got it set right anyway. Forza Apex was ok, but I hate the constant tyre screeching and I seem to remember GT being much the same. Dirt Rally on PC is the most realistic by a country mile, but so damn difficult if you haven't got hours and hours to practice on the different surfaces.
I disagree on graphics though. 4k makes a real difference to me. Yes, the gameplay has to be there to start with, but when it is, 4k HDR really brings it to life. For my money, Dirt Rally is much more immersive than DC, PC and Forza put together.
Wreckfest is the gameplay king out of the lot of them.