With the headtracker it more felt like just a convenient input method for head position, whereas with vr, well, it's like you're really in the plane. It doesn't feel like there's some translation between me moving my head and the camera on screen moving.

The loss of visual acuity is an issue, but since I fly only GA this is not so much of an issue - I'm mostly looking out of the windows and try not to focus on the instruments, just like in the real world.

If anyone you know owns a headset (DK2, CV1, Rift), I'd highly recommend borrowing it and trying the free version of FlyInside (15 minute demo limit) to get an idea: https://flyinside-fsx.com/Download