The most important thing to consider, like with any new game platform, is software. Developers have had access to Rift devkits for 3 years now, HTC haven't been getting enough devkits to developers and they've only been available for, what..? A year at the most.
And then you've got to consider the Oculus-funded exclusives - EVE Valkyrie, Lucky's Tale, Chronos, Edge Of Nowhere and The Climb.
And if that wasn't enough then you've also got to take into account the fact that if you own a Rift you can buy and play games from the Oculus Store AND Steam, whereas if you buy a Vive you're limited to buying Steam games only because Valve aren't playing nice with their SDK and won't allow Vive games on the Oculus Store.
Content is King at the end of the day and the Rift is going to be the best at that, at least in the beginning. There are supposed to be 70 Rift games/apps/experiences and only 12 Vive games/apps/experiences on launch day.

/