I'm not a fanboy of any description. I bought myself a Rift instead of a Vive because the Rift has so many more advantages to it...and these aren't opinions, they're facts.
- Lighter and more comfortable
- Easier to setup
- Sharper and clearer display
- Slightly less SDE
- Larger sweet spot
- Less chromatic abberation
- A bigger and better native software library
- Great quality built-in headphones making it A LOT easier to put on and take off
- ATW and ASW allowing for better super sa,pling and lowering the specs needed for a Rift-capable machine
- No interference from reflective surfaces
- It looks like a consumer-ready product instead of a devkit
- Better designed motion controls, they feel like an extension of your hands and the Grip buttons are in a MUCH better place
- The motion controls have finger tracking
- £20 cheaper
- A larger tracking area
- Slightly less noticeable god rays
- More room for glasses wearers
- Currently better tracking of motion controllers (although this will be moot after a software update soon)
- The Vive Puck allowing for better training in work and sports cases
Of course you may have the opinion that comfort, display quality, ease of use and quality of native software aren't issues but the majority of people I would say feel different.
HTC and Valve are continually playing catch up with Oculus and the Rift with ATW (and soon to be ASW although I don't think we'll see Valve implementing that until the end of the year), built-in headphones add-on with a more comfortable strap and finger tracking on their next controller design (assuming that they don't change their design the way that Oculus did when they realised that everyone was throwing their controllers around the office lol).
Which comes to another advantage that I didn't list above - Oculus have been working at this VR lark for years longer than HTC and Valve in terms of R&D, which is why the Rift has so many advantages over the Vive.