I've used OR and Vive, but not PS VR. I've got to be honest, the latter being on a closed system is a huge turn-off.
With PC based VR, the possibilities are immense. As soon as OR dev kits were out there were some amazing home-brew experiences to be had. Tonnes of existing PC games have been or can be modded to work in VR. Games like Skyrim/Fallout, GTA V, Half Life 2, Elite Dangerous....
Vive was the best experience visually, and can do everything OR can do and much more. Right now I can't see a reason to go for anything else. The only thing you'll miss out on if you can't afford more than one is PlayStation exclusives, but I think there's a serious possibility that PS VR will go the same way as Vita and Move....