I have a PNY 980ti (hybrid, water-cooled). I went for hybrid, to keep noise down. I went for PNY to keep the price down. So far, its been a good card, its silent when not in heavy use, and reasonable when cranked.
in 4K, I can mostly get 60fps from ED. On planets, it can dip though to 45fps ish.
I also have cash available to buy a 1080, but... I just cant really justify it to myself. My current card is only a year-ish old. It cost £600, do I really want to pay £700 now, to get +15fps on planets?
Personally, id rather wait to see what happens with 1080ti models. After all, why not wait 2-3 months, and get more speed for similar price to now.
In terms of ED tech. What could actually happen to justify a 1080ti?
Well, we know that a 1080 alone, will do 4k in ALL ED engine areas at 60fps. So a 1080ti is overkill for that.
Will we see temporal anti-aliasing in ED soon? Probably not (PLEASE FRONTIER DO IT FOR END OF SEASON 2!).
OK, what about planetary landings, or space legs? Probably both a good year off as well. But if we do see either, then a 1080ti might come into play to keep fps at 60.
IMHO, the biggest grunt soak we could see in the near future is Temporal AA. It requires more processing and data store. But the result is amazingly good AA (which ED sorely needs) and it also opens up the door for other real-time effects that are normally movie domain, such as Ambient Occlusion, Reflection Occlusion, Bounce Lighting, etc.
But for now, I think waiting to see when the TI is launched would be prudent.