I have the Rift, Rift S, and Reverb G2. My PC is a very old i5-4690K (built in 2014) overclocked to 4.4 GHz with 32 GB of DDR3 RAM and a standard 1080 gpu. The G2 is clearly an upgrade over the Rift S in most ways. The resolution and image quality is unbelievably good.
I am blind as a bat without glasses. Because the lenses have to be so thick, I use the highest index materials available and have the smallest possible frames to get the thinnest lenses. I have worn my glasses without many issues on all three VR headsets, though the original Rift put pressure on my glasses which pressed on the bridge of my nose, causing great discomfort if I flew VR for long periods. The larger sweet spot of the Rift S made it easier to use glasses than the Rift. The Reverb G2 generally fits as well as the Rift S, though I have to be a little more careful to get my glasses and the headset lined up for 20/20 clarity.
I only have a few complaints about the G2:
1) Until I build a better PC and get a stronger GPU, I have to give up frame rate to enjoy the superior image quality in some applications (principally DCS World).
2) The combined Windows Mixed Reality / SteamVR interfaced needed to play flight sims is in many ways a downgrade from the stability and performance of the Oculus app.
3) I see more head tracking errors and glitches in the displayed image such as flashing, tearing, etc. than I ever saw with either Rift.
I do see some advantages to WMR over Oculus:
1) I don't need the VR controllers at all. I can use a mouse in the WMR "home" and it remembers the virtual desktop. With Oculus, I never wanted to use the controllers, especially since they eat batteries even when they aren't being used, but I had to briefly put in a battery to open the virtual desktop every time I started the Oculus app.
2) I can use the voice commands "flashlight on" and "flashlight off" to toggle a small circular pass through window at the center of the field of view. This allows me to see where my rum-and-coke is and operate any controls I am having trouble finding by touch/muscle memory, while still allowing me see the what's going on in the sim. Oculus enables pass-through via a controller button and it covers the entire field of view. I don't have a battery in the controller to use the button and there was no real advantage to just lifting the headset up a bit to peek out compared to the hands free voice commands of WMR.
While the G2 image quality doesn't quite match the experience of playing on a large 4K flat panel, it isn't too far from it. But even if I get a high end cpu and gpu, all that will do is lock the fps at 45 with the kind of quality settings I want. I pretty much had the Oculus locked at 40 gps in sims, but ASW would cause ghosting of the target in a close-in dogfight. The G2 has a lot less ghosting... almost none. But at 30-45 fps, the image can be choppy when turning your head or rolling the aircraft. Aside from the ghosting of the target, the Rift S always looked smooth and natural in ASW. I am hoping a combined PC/gpu upgrade will solve all my problems aside from still being too slow to run 90 fps with high image quality settings.
Whether you already have a Rift S or you are trying to decide whether to buy a Rift S or a Reverb G2, I would go with the G2. Oculus has largely abandoned the Rift S and of course requires you to link a facebook account to use it. The G2 is in most ways superior to the Rift S, and it can only get better as PCs and gpus become more capable and the WMR/Steam VR combination is constantly updated to refine stability, performance, and image quality. Another thing to consider is that the audio and mic on the G2 are way better than the Rift S. But the Rift S isn't too much inferior aside from display resolution and it is probably a better choice for older/slower PCs/Gpus.