A few months ago my son and I tried out a full-blown Oculus rift at a buddy's office, so we have that experience under our belt too.
Here are some early VR observations.
AudioNo surprise coming from me, but the better the audio, the better the experience. The Google popups just use the tinny Pixel phone speaker during their demo. You get a sense of the visual/motion experience, but audio is severely lacking. I didn't realize just how lacking until trying out the Facebook goggles; they use Sennhieser over-the-ear headphones for their demos.
The experience is severely hampered unless you're using good in-ears/over-the-ears for sound. To drive this point home, my daughter tried my Google Daydream setup at home and was impressed. However, after walking out of the Facebook experience, she was completely blown away and indicated she wanted that setup for Christmas. When we got home I put some good headphones on the Google Daydream setup and she was just as happy. It's all in the audio!
Video/Picture QualityThe full-blown Oculus rift trounces the more accessible Facebook goggles and Google Daydream/Pixel setup. But, before you go out and acquire that scenario, it requires heavy tethering to a GPU/CPU intensive PC. I'm not into VR enough to warrant that kind of setup; besides, it would guarantee rotting away on your couch as you'd literally be stuck within a few feet of the immobile PC. I'd say second place in video is the Facebook goggle setup, but, again you appear to still be tethered to something. The demo's my daughter and I did had a cable that routed behind the wooden divider. That struck me as odd, but given the device's Oculus roots, I guess it made sense.
Re-CenteringThe Oculus device seemed to have near-zero issues with staying level and centered, whereas both the Facebook goggles and Google's Daydream do need to be re-centered (push of a button) every so often; not a big deal.
In-Hand Pointing DeviceThe Oculus I used didn't have one, nor did Facebook's goggles. The Google Daydream setup includes one and it makes a huge difference. I can't imagine driving VR without one.
AppsThe Facebook demo representatives controlled the canned experience, so there's no way to know what the app ecosystem looks like yet. I haven't played with Oculus enough to judge that either. With regard to Google's setup, they have a foyer app, Daydream, which acts as the stage to all the other apps (and there are many). Google's ecosystem is definitely up and running and seems to be doing well.
My favorite apps so far are Google Street View and YouTube VR 360. I'm using VR to experience things apparently, rather than to play games.
There is plenty of content out there advertising itself as VR, when in fact it's just a flat image/video (you can call anything "VR"). If you dive into this stuff, it's really all about the 360 degree content, so search for "360 VR whatever".