so what happened with CUDA magic on ETH?
Amd memory access is better (specially when you can mod memory straps), that why eth is better on amd, core performance is better optimised with cuda (and nvidia have more speed), that why zcash is better on nvidia.
...or should we say, AMD cards have better memory performance under 2GB but have troubles reaching 2GB+ regions. Unless they really going to fix it in their drivers, I'd say overall nvidia has better memory perf.
Now we are getting somewhere, ETH is more memory speed oriented, of-course core speed is important too, but in ETH memory speed is "more important" with better memory access from miners, amd is doing more MH than gtx, while (Branko was right) in ZEC core speed is "more important" (even on paper gtx have faster core speed) with (better optimization on) cuda gtx is better.
AMD has confirm that they did fixed dag problem.
