Both have a 2160x1200 display.
I'm curious which headset will be a) more comfortable and b) offer superior stationary head tracking. The room-scale tracking on the Vive is nice, but I'm thinking most people will prefer whichever has superior stationary tracking.
Supposedly the integrated headphones on the Rift will approach audiophile-grade quality. The Vive is shipping with earbuds, so presumably less fidelity there. Personally I wish both would ship without any audio equipment at all since I'm just going to use my existing headphones and microphone.