Really cus my G1 does 500+ easy. Im pretty sure if you get your hands on a good 1070 it could come close to a 1080 maybe within 5%.
Mind you electricity for me is free though but I dont want to invest a lot (wont be buying the Vega cards anytime soon).
I'd stick with 1080Ti or 1070 and forget about the 1080.
I have never seen a 1070 that managed more than about 460 - SPECIFICALLY INCLUDING my Gigabyte G1 cards.
You apparently have one that handles a lot higher overclocks better than most do, or you're looking at the "momentary peaks" and counting those as the hashrate where I tend to look at the AVERAGE hashrate instead, or you're in a VERY COLD ambient temp with your cards - or a combination of all 3.
Even with minimal tuning and having "fairly high ambient temp cooling" limitations, most of my 1080 cards easily hit 530 and I suspect when I take the time to fine-tune them they will be able to push closer to 550 - and NONE of those are "high end" 1080 models, most are the Zotac Mini or the bottom-end Gigabyte 2-fan models which are definitely heat limited in my environment.
On the other hand, with 1070 pricing getting back down into the pre-gouge range, the 1070 is starting to look like a better option even at the system level to the 1080 in many respects - and the recent climb in 1080ti pricing isn't helping any.