I only have a 980 so I am not sure on the exact numbers. Technically there shouldn’t be any difference as both cards support Direct Compute, so if there is a difference it shouldn’t be very much (10% max imo).
Don’t quote me on that, only a guess, but DC is DC so it shouldn’t matter. We had a Nvidia dev answering questions & implementing it all over in this thread if you want to read more (includes other Nvidia specific tech like Flex, WaveWorks, Hairworks, etc as well):