Check this video out:
https://www.youtube.com/watch?v=GQzERnxQpY8&feature=g-vrec&context=G20bf236RVAAAAAAAAAQ
From my POV, so far rFactor 2 runs very well, and handling is excellent. It does take a lot of time to get used to the tire physics, but this has added a whole new dimension to the realistic effects. So far Force feedback feels great on my old Momo. Graphically it's not that great, and seems to still be using DX9, but this is something they are working on in the final stages of dev. The interface has changed a bit, but not much compared to rFactor, but it's probably more for the familiarity of the game. The incar sound is great, but replays, not so great, and the spotter is barely audible, so I hope they are also working on the sound.
Project cars does look very good, warning, this game may not run on older machines, but I see they now have set it so you can run the game in DX11, or otherwise (not sure if DX10 or DX9). But still, I had to ramp down the settings on my machine, So maybe Prod could benchmark on his beast. The interface seems a bit clumsy to me, so I really hope they work on this. And the physics seem OK, but there is something not quite right, I haven't had much time to play around on this game, so maybe I'll figure it out some time. So far there are no race customization options, so you can't setup a race weekend where there will be multiple sessions (practice, quali, race). Maybe I just haven't found thos options yet, like I said, interface feels clumsy. I'll need more time before I give a verdict.
The video also mentions iRacing, maybe sometime I'll check this out too.