I've experienced not-so-solid tracking on the Oculus Rift CV1 with a single Constellation tracker when facing away from the tracker.
On the other hand, Tested.com reported in their HMD comparison that they have seen better tracking performance by Oculus than the HTC Vive. They are one of the few people seeing it that way, however - most reports indicate that the Vive tracking is superb.
Whichever headset you buy, if you are aware that it is a first generation product and can live with the high price, you will not be disappointed.