After using both during a few weeks for me there is only one clear winner: Oculus Rift, and let me explain my reasons for saying this.
Five key points:
1. Products are compared poorly. We must compare the HMD on one side and the controllers in the other. Since Touch will not come until September, we must remove Valve's "cutlass" controllers from the comparison. We must also take concepts as room-scale outside the comparison. Both Rift and Vive allow room-scale. Simply games for Rift are more focused on playing seated. But that will change with the arrival of Touch. We have to compare pears with pears, so I will focus on comparing the two HMDs and nothing else, which for now is what Oculus has released.
2. Focusing on the HMDs, there are four key aspects. First is the arrangement of pixels. Rift is noticeably better what means it feels to have higher resolution than Vive, and also less screendoor effect. It is quite remarkable, not slightly. For example, in a game like Elite Dangerous it means that in Rift you can comfortably read the interface panels and in Vive you need to lean forward. It is a very noticeable difference.
3. Ergonomics. Absolute Zero for HTC Vive. Vive in my opinion is a Developer Kit 2 put in a nice box. It has the same ergonomics as the Oculus DK2, I mean, painful. Weight badly distributed that causes that after half hour of play my cheeks hurt, where all the weight is supported, and it hurts my head. From the backside there go four wires attached! (yes, yes, four), which form a rigid assembly pulling you down and creating an enormous discomfort in both standing and sitting experiences. Sitting is even worse. The absence of integrated headphones is very noticeable and it is a mistake. Putting them on is a nuisance every time you use the HMD. Rift is more rigid in its foam, but on the contrary it feels super light on the head and it don't press your face at all. This allows a huge difference in terms of hours of use. I have played up to two hours at Rift without any discomfort symptom. With Vive, half an hour and I'm in trouble.
4. Lens glare. This effect of Fresnel lenses is equally pronounced in Vive than in Oculus Rift. Both share the same problem. In games with high-contrast black backgrounds with bright interfaces, such as Elite Dangerous, it is a problem that is very pronounced and very annoying. You can only reduce it by decreasing the brightness of the interface, but even that way it pops out. This is no better in Vive than in Rift. Both equally bad.
5. The most important point in my opinion, the one and only that leave in nothing previous three, is the Async Time Warp, the wonder created by the genius John Carmack. HTC Vive does not have this technology and it is super noticeable. I have done tests on a PC slightly above the minimum specs required by Oculus and Valve. The card I've used is a GTX970. In Rift all games are extremely smooth, even the most demanding, as Elite Dangerous or Project Cars. Never, never I have a drop of frames. In any moment. With HTC Vive sometimes there is judder. Not a judder to stop you playing, but there are moments in games as Elite Dangerous when entering a space station where definitely the wonder created by Carmack shines in all its glory. A GTX970 is enough to play Elite Dangerous in Rift, but not in HTC Vive.
All my current experience, both sitting and standing, both installing, buying games, settting options, etc. Everything is comparatively better in Rift than with Vive. The only plus point for HTC is the tracking system. It is very good. The sensors have a huge tracking volume and are very accurate. Oculus camera, although is great for being just a camera, is below. But also consider that HTC Vive are two base stations that must be placed in a very specific position in the room, and that is a hassle installation.
Overall, after two weeks of testing with each other, I have a clear winner. Oculus Rift. There's no more. I only can say that from now on, except for games or apps only available in SteamVR, I'm going to enjoy the rest in Rift. And I am convinced that when Oculus releases Touch most of the content that is now exclusive to SteamVR and is only room-scale oriented will also be available for Rift. So I have no concern in that regard. Oculus is not going to be as a device with a fragment of the content of VR. Developers are super eager to get their creations to the widest possible audience.
I do not do this analysis in order to alienate anyone from the idea of purchasing the product from HTC. I only expose this as informative, but I recommend to anyone who is in doubt of what product to buy that if he or she has a way to test the products by a friend, do it, try the same game in both headsets, and evaluate calmly after a long gaming session which product you are interested in more. Rift and Vive are expensive purchases. My advice if you are in doubt is to have patience and seek the opportunity to try and see if what I say in this analysis is true or not. I've read dozens of reviews and each makes an assessment putting pears and apples on the table. There are those who appreciate the room-scale above all things, and of course that is a feature with limited support in Rift since it only gives you one sensor and HTC Vive carries two. If all you want to experience the VR is the room-scale, then surely Rift disappoint you. But in my opinion, that is not the way to do an objective review of the products. We have to compare what is now available in both products, and within that, evaluate all what they offer, from installation, to purchasing of content and using the content. Again I recommend to not trust any review, including this one, and please, try first hand the products before buying them. Perhaps if you are patient and wait for Touch you end finding that all Oculus products (HMD, sensors and controllers) are better than HTC equivalents. And that would make worth the waiting.