Edit: Upon further research, these are business/enterprise only, so they are not competitors to the Quest which is consumer first.
On Reddit, there has been some coverage of those headsets in the past, eg [4], [5] and [6], but it's easy to miss. I still find headset analysis from VR YouTuber the best.
Also not all tracking is equivalent. Some headsets released by companies are truly atrocious.
[1] https://www.youtube.com/c/ThrillSeekerVR/videos
[2] https://www.youtube.com/c/Tyrielwood/videos
[3] https://www.youtube.com/c/mixedrealityTV/videos
[4] https://www.youtube.com/c/VirtualRealityOasis/videos
[4] https://www.reddit.com/r/Vive/comments/7cs6jc/htc_vive_focus...
[5] https://www.reddit.com/r/oculus/comments/ektig3/first_new_vr...
[6] https://www.reddit.com/r/virtualreality/comments/hjymnn/pico...
On the other hand, I have had some headsets that were "truly atrocious". The Meta 2 was one. Never before or since have I had an AR headset give me simsickness. The PiMax 5K, with its nasty distortion at any view angle beyond the ~100° average of every other headset and its sole raison d'être, plus red image static, plus janky sidecar driver program. The Pico Neo 1, where the facial interface cut painfully into the bridge of my nose (I have it on good authority that the 2 corrects this issue for Western markets).
I was super disappointed when Google canned Daydream. I thought the Lenovo Mirage Solo was way ahead of the market.
The Vive Focus's controllers are a little flaky, but not unusable.
The original HoloLens was way too heavy, way to narrow of FoV, way underpowered, but hand tracking and built-in voice recognition, and MR desktop metaphor was quite something. I have yet to get hands on the 2, so I'm eager to get one. There's a quality of life experience with the software and the development lifecycle that is really, really missing from every other platform.
My point is that we should legitimately ignore the terrible headsets, but try to be a little more forgiving of the flaws of other the "not best-of-the-best" headsets. We absolutely need market competition in headsets. We must not allow Facebook to dominate VR. That is their end-goal, after all, and it would certainly be to the detriment of us all.
Tracking-wise, there isn't a lot of difference. Certainly not enough to warrant giving all your data to Facebook.
The Quest stands out because the tracking is as accurate and consistent as on desktop class VR headsets. The software and user experience is a clear notch above any other standalone headset.
[0] https://www.scribd.com/document/399594551/2015-06-22-MARK-S-...
I think it might already be too late in terms of dominating.
In general though, I agree. There needs to be more 6-dof standalone headsets. I'd love to have a standalone WindowsMR headset. Something like HoloLens with lenses and OLED displays instead of the waveguides.
The Quest is pretty good, but it's not all that great to think that Facebook is an unbeatable juggernaut. Hell, all of the standalones (3-dof or 6) are still only running the Snapdragon 835 Mobile (not much more than clones of Qualcomm's first VR headset reference design), where the 855 and 865 have tracking on-chip. The 835 is not actually all that great for VR (it's what's running in my now-ancient Pixel 2), it's just the only SoC that hardware vendors have put the effort into. Hell, Qualcomm has two SoCs specifically for XR that nobody is using.
EDIT: correction, the HoloLens 2 is running on the 850 Compute Platform, which is mostly the same as the 845 mobile.