My Game (AHIII) locks up when I exit an Arena in DX9 version but not the DX11 version.
It is only the game that locks up on me and I can force it to close from the taskbar or the task manager.
I honestly can't tell the difference between the two versions. I run 6070x1200 on Max settings with shadows and sometimes reflections (depending on the ride) disabled.
The only time I dipped below 60 FPS is during a mass take off in Saturdays Scenario ... I think I got as low as 47 FPS.
I'm running on a Xeon e3 1231 v3 with 32gb DDR3, EVGA gtx 1080ti OC and a Sound blaster Z on windows 10 pro.