Too early to tell, can only go from impressions and experience.
Ignoring experience, since I only know the DK2 and would by default be my choice, my impression is currently:
1. Vive
2. Rift
3. Morpheus
If Morpheus works on PC with the camera and move then it goes straight to the top. Being able to play on both platforms make it the most logical choice, it looks cool and impressions are great. It is also coming out later than the other two and I may not be able to resist that long to make an informed choice. I will probably buy Morpheus no matter what eventually unless it turns out to be hot garbage. Being a locked in experience can benefit Sony hugely if they enforce standards, a 60fps standard seems way too low even with this tween technology to bump up to 120Hz. If they made it 75FPS and pushed it up to 120hz then I would be a bit more confident. Although impressions aren't negative so who knows.
If Rift announce hand controllers coming with it bundled as standard then it goes to the top unless Morpheus supports PC, or Sony for some reason allows the Rift to work on the PS4. Also the camera or whatever motion tracking they use in the end has to be better with a wider angle for what is a PC device so a desk environment.
If Vive has some kind of free moving solution for the wires and does what has been said then it is a great competitor. My main problem is actually Valve, I hate Steam, I hate absolutely everything about it and what it has done to PC gaming. It literally drove me away and I think PC gamers are incredibly short sighted on them as a company/monopoly. Not to mention the master race cult BS that comes along with it. I don't want DRM, I don't want to be locked into one platform so if that is the case it goes to the bottom and will never consider touching it. Not to mention they are incredibly incompetent, the teabagging experience of Half Life 3 is somehow given a chuckled pass compared to say the last guardian. Sony may leave Morpheus to die but there will be some software support and are good at getting software out. Valve, unless they have been developing exclusively for VR all this time will likely have one or two things to support it then go back in the shadows. All that said, the kit looks and sounds great. HTC build some incredible devices.