The guys at MotoGamesTV have put together an interesting comparison, showing the Toyota TS040 in Project CARS and Forza Motorsport 6.
Even though the car models are slightly different between the games, with Project CARS featuring the 2014 version and Forza having the slightly-revised 2015 model, the comparison still allows a close look at how visuals, sounds and details compare.
The video shows a lap around the Circuit de la Sarthe, home of the Le Mans 24 Hours, that can be raced with a full day & night cycle and dynamic weather in Project CARS while Forza Motorsport 6 has fixed weather.