My personal take away is if you are going for the maximum immersion, have space and the money, go with the Vive or Vive Pro. The Rift (likely applies to Rift S as well since they are so similar) was more comfortable than the Vive for me at least and I liked the controllers more but the tracking quality was not as solid especially in even medium sized rooms. The visual quality on the Oculus is not quite where the Vive is either. Additionally the Vive is a pretty open platform so there are lots of third party accessories you can play with (once again if you can stomach the costs). I love using Vive trackers on my feet to track my foot motion so I could run in place in games to move. That kind of ecosystem doesn’t exist for Oculus. Additionally Valve will likely release new controllers soon with full finger tracking (and then you could use your old controllers as Vive trackers)
Between the cost and the PSVR-style hard headstrap (big improvement in comfort) I'd recommend the Rift-S strongly for consumers even though the Vive Pro is preferable for researchers.
Oculus's tracking system is outside-in, the stations in the corners of the room are cameras, and the headset has infrared lights on it. You need three base stations, and they all need to be connected to your computer in addition to the connection for the headset itself.
Oculus has arguably nicer controllers (grips vs wands), but Vive is launching "knuckles" controllers soon so that relationship might flip.
I chose Vive because of the close integration with Steam, easier setup with fewer wires, and more titles (at least at the time, idk about now).
The screen door effect doesn't bother me, so the main feature of the Rift S isn't a draw for me.
The Vive/CV1 have lower resolution, as they are older devices. They are equivalent or better in all other aspects (the Vive has an OEM wireless solution using WiGig, but is isn't as cheap as I'd like).
The Rift S has higher resolution and therefore less screen-door effect, which is a MASSSIVE deal. Despite the following criticism, resolution does make the choice genuinely hard. There's nothing else special about it, unless you intend to have a mobile VR setup. The supposed benefit of inside-out tracking is the setup complexity, but one hour once-off is a substantial cost to pay for substantially inferior technology. My fireplace can interfere with the lighthouses: you get yanked right out of the experience when controller tracking is lost, it is awful.
There's also the Pimax, if you don't mind looking ridiculous and having a pretty heavy device strapped to your face.
My best recommendation is that VR is like furniture. You have to try it before buying it. Try and find a store that has demos of the devices and see which compromises you prefer. Spend at least 30 min in each. Just keep the setup time of the Vive and CV1 in mind (it's not hard, just time consuming). The CV1 also devours USB2 ports.
Honestly, if you've got a PC that can handle it and you want to try some high-quality PC VR titles, the Rift S is probably a pretty good choice. Otherwise, if you're looking for something cheaper, you can often find WMR headsets on sale for ~$200.
However personally I mainly decided against Rift because I do not want to support their parent company (Facebook).