The GT500 pack is excellent, some of the best feeling cars in the game by a mile. Okayama/Takamiya is excellent as well, always loved it in iRacing and it is just as good here.
I had a chance to A/B the game on my PC rig during the free play weekend and the results were as expected, I compared it to AMS2 and it simply doesn't hold a candle to the more established game. Using the GT 2004/5 cars in both, racing on Spa, PMR was fine, jus a little frustrating and inconsistent with the AI behaviour being somewhat erratic, the car sometimes randomly snapping without warning (used the Murcielago R-GT in both games). AMS2 just felt a bit more alive, cars broke traction more naturally and responded better to being pushed. The AI are also better in AMS2, far from perfect, but I felt I could trust them more wheel to wheel and when going for a pass, they don't try to turn in anyway, they occasionally make contact, and that player to AI contact is where PMR has an edge, in AMS2 you tend to bounce off and spin while the AI is unaffected. In PMR the cars are a bit more robust to contact.
Visually AMS2 is superior, the lighting, level of detail, reflections and track detail are much better than in PMR. The irony being that AMS2 runs on Madness engine which powered pCars. PMR has improved with 2.0 but the environments and overall detail still feel lacking and the cars don't sit in the environments well in my opinion.