There are pros and cons for either headset tbh.
The Oculus Rift and Touch bundle for $399/£399 would be your best bet. It’s 200 notes cheaper, it’s more comfortable to wear and has built-in headphones (unless you spend the extra $99 for the Vive Deluxe Audio Strap),the displays and optics are better (less SDE and the displays are sharper and clearer) and you don’t need to drill holes in your wall to mount the Lighthouse base stations that the Vive uses.
If you’re developing a Room Scale game you might need to buy a third sensor which are $59/£59 but you CAN have Room Scale using the two supplied sensors in opposing corners with only a few minor tracking hiccups here and there.
With the price difference being $200/£200 I can’t see any reason why anyone would want to get a Vive over a Rift unless they have a SERIOUS problem with giving Zuckerberg money.