i heared that too . but any way if it was slower at some ones machine its not a must that it would be slower at yours too .
so its up to you try both of them and use each time any program that could check your cards productivity then you will be able to tell if its really slower or not.
They may be slower for some than the 1080 drivers, I've heard this also. But they are faster and better looking for me than the 1080s. I really like the 11o1 s and I am extremely satified w/them. Test them both, as mr2000jp said, and decide for yourself. Best of luck.