1070 TI vs 1080 TI for VR

Take 1070TI or something cheaper :)

I used Oculus Rift CV1 on GTX 970 and games run well, but VR gear itself on curent gen is still not something that I will recommend.
on example Oculus rift CV1
Positive:
Tracking
VR experience ;)

Negative:
Ghosting like hell ;)
To low resolution for my taste games look smother even on 1080P Display
I needed use contact lens * Not glasses friendly
Dust inside lens :**(

In end I sell my Oculus Rift CV1 and end my experience with VR for now I probably buy gen 3 when arrived in distant future current we gave gen 1.

It depends too much on what you're going to run. If you want pure math answer then yes, 1080 Ti will always outperform 1070 Ti, but by how much, that's up to debate. It can be a lot, but it can also be a super small difference.

I wouldn't say that you need 1080 Ti if you already have 1070 one. Sure, if you were about to buy, then that would be entirely different discussion, but if you already have it then I don't see any logical reason to switch for better one, it's too small and insignificant difference to justify price. I'd rather wait for next-gen at least and consider then if your 1070 experience won't be as good as you expected.

I think the limiting factor on how good VR looks is really the headset, not the gfx card. If it's another 400 euros for you to go for the 1080ti, I wouldn't bother.

I'm using a standard 1080, myself.

I had a GTX1080ti and it was great with a Vive.
You can enable supersampling and that does help things look better etc, but whatever VR set you go for atm you will have the screen door effect. (unless you use Pimax, but as above the tracking etc is not so good)
I sold my 1080ti in preparation for the new gen cards out in the next month or 2 though...

1080 ti cards are 'down' to 800 - 850€ again (at least over here in DE) so if you can afford it then go for it!

sadly they bench only in 1080p but the 1080 ti should be around 33% faster in general.
http://gpu.userbenchmark.com/Compare/Nvidia-GTX-1070-Ti-vs-Nvidia-GTX-1080-Ti/3943vs3918

anyway you want all the speed you can get when running VR or a 4k display.

It largely depends on what you're planning on playing in VR. For general VR games that are built for VR from the ground up - like Robo Recall, Lone Echo, The Climb, SuperHot VR - an RX 480 or GTX 1060 is fine. For something like Assetto Corsa / Project Cars, or even Euro Truck Simulator, you'll want the most powerful video card you can afford.

As for VR itself, I wouldn't recommend it at present. I got to try a Rift for a few weeks, and it was a nice novelty but not something I feel justifies the cost at present. SuperHot VR with room scale was amazing for a few hours, but not something I'd want to play over and over again. The Climb, with the touch controllers, was awesome and I was surprised by how my arm and back muscles tensed as if I was actually climbing. A session in The Climb gave me an upper body workout, and that's a game I would gladly play again, but it's really the only one.

If you have the money to burn, go for it. If you're on a budget, I'd hold off. The low resolution and screen door effect of the Rift and basic Vive become really apparent with more cinematic games such as Lone Echo, where I often felt frustrated because I couldn't make out what the game expected me to be able to see. The Vive Pro is much better in that regard, and largely resolves that issue, but you'll definitely want a 1080 Ti to power that monster. But given how expensive it is, I can't readily recommend it to anyone without money to burn.

Aren't they supposed to be announcing the newer stuff in the next month, maybe two?

I would wait for the price drops then look into it, unless the mining craze has them insane too.

Edit: Nevermind, AMD stuff isn't due to Q1 next year and no clue on the new Nvidia cards.