If you read some forums, the consensus is that 180° 3D is the way to go. People are not happy with sites that produce 360°.
One of the problems with 360° is the quality. You're using the same resolutions for an even larger area.
4K in regular porn is super sharp, 4K for VR comes out just okay, since it's not the actual resolution that your eye will see. With 360° it's even worse. And you cannot raise the resolution further, because today's devices won't be able to play the files then.
It's not really worth it to waste the resolution for stuff that's going on behind your back, I don't think people generally want to spin 360° while watching porn either.
I think some sites "solved" the quality issue by recording 360° but not making it 3D. (Your left and right eyes see the same picture.)
Well, users aren't happy when it's not 3D either.
Also, anything that's not close to the user in the VR world is just not detailed, and not enjoyable. So people fucking meters away is not really enjoyable.
If you want to learn what users want, reddit is the best place to be. They don't want 360° orgies. They want intimate 180° 3D videos, with the girls being super close - girlfriend experiences, eye contact, actual kissing, boobs in the face, face sitting, stuff like that.