Honestly, my answer is probably all of them, but I'll still try to pick a favorite from the little info we have.
Just to be clear, I've been into VR since the early 90's. My first HMD was the original Virtual i-o glasses, and I thought I was king shit showing those off to my friends. I eventually got a VFX1 and about a dozen others. I ended up befriending Palmer when he was just tinkering with shit in his garage, and got him to mod an old Liquid Image HMD for me. He ended up doing way more than modding it, and it became his first named prototype that would eventually lead to the Rift. PR1. This was FIVE years ago, and I thought it was the best thing on the planet. It weighs at least six pounds. It is absolutely insane how quickly VR has improved in just FIVE years. Seeing all of these HMDs and watching the big names dive in makes me so incredibly happy to be alive right now. My childhood hope of real VR is finally coming to fruition.
Right now the Vive is on top because of inside-out positional tracking, imo. The HMD itself actually looks pretty bad for a consumer HMD of this caliber. It uses the elastic straps like the DK1/2 used, and there is no counterweight at all. I really hope I am wrong, but it just looks like it would be uncomfortable to use for more than a short period of time. Hopefully the consumer version will improve on the ergonomics, because if the positional tracking is truly 15x15, I am going to want to use this for a while!
Morpheus has the coolest design to me so far, even though I have not been lucky enough to wear one. But you can tell it definitely looks like something you could pick up at Best Buy, and not a developer kit. It's sleek. The latest specs are actually pretty awesome, too! The panel may end up looking slightly better than DK2 with it's RGB display, and the refresh rate is nice! I think it will end up being a great HMD for PS4, and I will probably have to buy it.
The CV of the Rift is the biggest unknown, because we don't really know what kind of features Oculus is waiting to reveal. I know they have said in the past that the camera for positional tracking wasn't indicative of the final product, so I am not sure if they are going to have a system similar to Valve's or not. I hope they do, because I think VR shines the most when you can navigate in the virtual space just by moving your body. I also think with the acquisition of Carbon that we are going to be surprised at how sleek the CV1 will end up looking. I am hoping it can compete with the Morpheus on that front. I seriously doubt it will end up looking almost exactly like Crescent Bay. I really think they will nail the final design. In the end my biggest hope for the Rift is the improved positional tracking space. The thought of Valve's 15x15 tracking area makes me beyond excited to have it.
Sorry for the rambling, I just get really excited talking about VR stuff.