Vive could be used very well for room-scale and sit-down VR out of the box. If you need more sensors and extra controllers or whatever you have to count into the price as well.
I’ve tested both with UE4 and both work well. Rift is nice. But if I would create some roomscale VR game then I would use Vive. It was created for kind of VR (including controllers from beginning) and the room scale tracking is amazing. There are still very few VR users (and it seems it’s not exploding soon) … there are some with Vive (that already got everything for roomscale when you buy from first day) and there are some with Rift DK2… and there are some with Rift final with Xbox controller and there are some with Rift that own touch … and maybe there are even a few that own Rift and touch and a second sensor or third sensor. If you create game for Vive you could put it on Steam and both (Rift+touch+2nd-sensor users and Vive users) should be able to be your customer. There would be some that own Rift and touch and a second sensor but still don’t like your game because they don’t like… fantasy… or lasers or… arcarde or… whatever type of game.