There is a free version of Project Cars as well, search for Project Cars Pagani Edition. Works well with VR.
I've tried them all personally (albeit briefly) and settled on Assetto Corsa. VR implementation is top notch, well optimised (90fps maxed out on my rig) and, above all, driving physics are supreme. Plus, unlike Race Room, Project cars etc, AC has tons and tons of street cars which I much prefer over racing contraptions.
The only downer with AC is that the main menu of the game is displayed on your monitor only, so you have to look through the nose cut out in oculus or invest in Virtual Desktop app. But this downside has an upside too as I can easily watch replays on the monitor, just by taking the headset off and switching AC rendering mode to single screen - without restarting the sim.