GTX 1070 or the 1080?

Currently i have a 970 and does the job but im stuck at the lowest settings of the game my cpu is working at 50 to 60 percent i checked my VRAM usage and its at the limit so the therefor i cant play on higher video settings.

Im currently multi-boxing with 10 toons sometimes 12 i cant decide what would give me the best result for the buck. i know that the 1070 is $200 cheaper in general but the 1080 offers more performance.

my biggest concern is will the 1080 be worth the extra money and out perform the 1070 by alot or i would be better off just getting the 1070 and save the cash.

boxing 10-12 toons
resolution is at 1080
CPU is an i7- 4771 i know u should;ve gotten the 4770k or the 4790k,
32GB of ram - i only use 20 to 22
samsung 840 pro ssd
GTX 970

They both have the same amount of vram, 8gb.
I don't know what kind of performance you're expecting, but I can share my experience.
I have 1080 in SLI and boxing 5 characters on 4k resolution.
It's really not how this works, but if everything scaled the same:
5 chars at 4k is as many pixels as 20 chars at 1080.
I have 2 cards and if the scaling was 100% (ie, 2 cards give exactly double the performance) then 1 card would give the same performance I get for 10 chars at 1080.
I play max settings on my main, and lowest settings on all others and get 60fps on main.
I am going to say this again, this is NOT how it's going to behave in reality, but it might give you a very rough idea.

My cpu is a lot stronger (5960x @ 4.5ghz) and wow is running from the 840 evo ssd with 32gb of ddr4 ram.

Just an FYI... If you upgrade the GPU to increase performance, the CPU load is likely going to increase with it. By how much is anyone's guess, but if you start increasing the in-game video settings, then the CPU will definitely need to work harder.

With that said, if you can afford the better GPU, then you should buy the better GPU, even if the cost-to-performance ratio isn't the best (which is usually always the case with top-tier hardware).

I think these two videos go a long way in helping decide, they've spent time looking at where the bottlenecks show up.

Core i5 Speed too slow for 1070, crushes 4690k in benchmarks
https://www.youtube.com/watch?v=s42gvVS77dU

How to Test for Bottlenecks in GPU and CPU to maximize use of 1070 and 1080
https://www.youtube.com/watch?v=zOGdWct6qtc

i end up getting a 1070 GTX.

What i notice is that the card is less CPU dependent my CPU dropped on avg 5 to 10% work load just by increasing the video setting... this game as a awesome surprise. I was able to turn a bunch of options on while before i could not.

The only issue is the 8GB VRAM still not enough for 10 clients im running the card close to the max VRAM, Im going to wait till the Titan XP comes to market so i can push the settings even further

i did not get the 1080 because the work load on GPU is minor i could not crack pass 35% so getting a 1080 would be a waste of money, now the Titan XP is interesting because of the higher VRAM

Im going to wait on upgrading my CPU because of the new AMD ZEN architecture with 8 cores and hyperthreading which should be equivalent to intel's hyper threading or at list close if not ill jump on the 6850k or better

970GTX settings was at 1 in all clients expect the main at 5... dalaran cpu work load was 80% to 93% outside is was ranging from 70% up to 90%
1070GTX the settings are at 3 with everything enabled to at list low and the main still at 5... Dalaran CPU work load is at 90% to 97% out side range from 45% to 60% at all times

i am very happy with the 1070GXT results and how it impact my game play way better than the 970GTX
the GPU clock never once hit above 1750Ghz avg was 1300Ghz with 33% GPU work load

Sorry for the long comment and thanks for comments above!