Sell 1070 gtx and have 2x 1080ti

[Isolar1s]

Can get a 1080ti for £700 gbp would it be worth selling my 1070 for £400 and buying the 1080ti. Would the hashrates make worth while to have 2x 1080ti instead of 1x1080ti and 1x 1070 runing

[Pekine]

You should not only look at the Hashrate, but as well to the Power usage and the algoritm you want to run.

You can check the power usage by card on whattomine.com.