The reason I prefer the Rift:
* I am in a cramped space where my desk is and it would be impossible to "move around", even just 1m from my desk.
* The motion controllers of the Vive seem *great*, but then Oculus Touch controllers will be out as well (soon). Means I can get a Rift cheaper initially and STILL get the Oculus Touch controllers when they're available. Means: The price is likely ultimately the same and the Rift has no significant disadvantage over the Vive.
* Availability of demos
One of the biggest incentive to me for the Rift is that I can go on OR forums and download lots of demos/games etc. people already made for the Rift. Some are said to be fricking amazing! If I get a Vive I wouldn't even know where to go to get demos!
* Both sets use the same panel, resolution etc. anyway
* Rift is said to be lighter and more comfortable to wear
I am NOT saying the Vive is "worse" or the Rift "better", not by a long-shot, but in my case I just think a Rift makes more sense. If you have a dedicated area where you can (and you want to) walk around in VR, a Vive might be "better" for you and of course the fact you get the two controllers already included. I DO see that having actual motion controllers would be awesome for more immersion...but as said Oculus Touch will be out too, so no criterion for me.