Kind of an off-topic response, but I'm leaning towards the Oculus Rift myself. Launching without SteamVR support ready was a really big mistake, IMO. I want to see, factually, how SteamVR operates, compared to the Rift and Vive, before I consider a WMR device worth a purchase (speaking as a Lumia buyer, I think most here can get my trepidation over software support on a Microsoft product).
Since WMR headsets are fundamentally different in how they track, I don't want to buy a device, only to find out the inside-out tracking leaves the controllers a bit less usable or limits SteamVR library support. I haven't gotten to read up on how stuff plays with WMR, but after reading that the controllers need to be in the FoV, I am disappointed. There's an archery Early Access SteamVR game named Quivr, which I imagine involves reaching behind one's head to draw arrows. How would WMR handle such an action in a SteamVR game (or the Rift's Robo Recall)? Too many unknowns to want to buy in. Plus, Microsoft is traditionally atrocious in pricing digital game purchases, so I'd rather know I can get SteamVR games at a discount than be forced onto the Windows Store until SteamVR support comes (Superhot VR is $25 on W10, but on-sale for $18.75 on Steam right now).
Haven't gotten to compare the Vive to the Rift, but really enjoyed my cousin's Rift, speaking as someone who generally sneered at it for becoming part of Facebook. That said, I'm still waiting on Vega to be available with aftermarket cooling before I do a new PC build, which will be for a VR headset. If WMR can get SteamVR support in the next 4-6 weeks (when I'll be doing the build), I will look at it for sure.
I'm really disappointed the ASUS headset got delayed. The idea it would use a single 3K display sounded really interesting, unique, and cool. IDK if I could hold out until it launches, I want to get a VR device sooner than later. However, I think they did the best job to differentiate in the market with the visual design AND that display setup. Can't say I'm too fond of the other WMR devices out now. I don't like HP, Lenovo, or Acer in general, which would lead me to want the Dell Visor, but I don't like the white on it. Samsung's is a pretty noticeable step up in price, and I'm generally not a fan of their displays, so I'd want to see that theirs doesn't have the traditionally oversaturated colors of a Samsung display before I pulled the trigger on that.
One thing though, I'm glad there are so many options. Microsoft did a half-hearted job when it launched WP7 under 3 device partners. That we've got 5-6 known, quality companies putting out WMR headsets can only be a good thing for the future of the platform.