Do you really prefer webcam + opentrack over the trackir? Asking because I literally have a trackir on the way to me in the mail, and most discussions I could find were at least 2-3 years old.
Edit: Oh, zero hardware on the head. Makes sense.
That said, I have had issues with opentrack that involved some mildly irritating troubleshooting. Namely X4: Foundations didn't work properly with the standard freetrack output regardless of how I configured it, and I ended up needing to use "UDP over network".
I've never had a comparable problem with TrackIR, in spite of using it with a wider variety of titles over a longer period. I do kinda like having it as a backup in case more intractable problems crop up.