The rift is the most known quantity.
As for the AR, only the Samsung seem the only to be comparable to it, but it also is not sold outside US\ASIA from what I gather, if you are in EU or most of the planet, no luck.
As for using the AR as a VR HMD you need it to work with SteamVR, this is coming but might take a few months, although it might be in early beta stages.
Mileage will vary in other words.
I also hear there will\might be a plugin set of cameras for the rift to be used as an AR set but that might just be some pipe dream thing.
As for VR, Pimax seem to be the talk of the town, but the KS campaign has ended and most likely they won't start selling publicly until this summer, late spring.
That would be a long time without VR.