of course the 1070 are very good not only at zcash but at lbry skein and a bunch of other algorithm, amd is only good at ETH, and i don't like to ahve only one choice, nvidia now is the king i think, better to go with the green side until vega come out
AMD is good at quite a few algo, not just ETH - they just happen to dominate on ETH on a hash/$ basis over anything NVidia, even though NVidia is very competative to slightly superior on hash/Watt on ETH.
For example, on ZEC and despite recent gains on the green side, AMD is still competative-to-superior on hash/$ though noticeably inferior now on hash/Watt.
The major DOWN side on Nvidia is that all of the algos it DOES dominate on have much smaller network hash pools (in number of cards) than ETH and ZEC do, so while NVidia has more options they are all much SMALLER options and tend to bounce around a LOT more on profitability (DGB is a major case in point recently, I've seen it bounce 3:1 on profitability in an HOUR at times depending on which DGB algo you are looking at).
It says a lot that there were a couple points in the last week that I was ballpark 0.2% of the entire DGB-skein or 0.5% of the entire DGB-groetsl hashrate with MY small number of 1070s (not at the same time though), and actuallly managed 1% of the total DGB-Scrypt network hashrate for one short period with my SMALL A2 farm.
There's more than 3 coins "the herd" flocks to, BTW - BTC ETH ZEC LTC XMR DASH all have major pools of miners, though only 3 of those are GPU mineable any more.
smaller network i think are good, because they keep away the big boy with their huge farm, it create a heaven territory for the nvidia guys, where they can have more profit than amd, i like to mien small coins with my few rig, i earn a lot versus those that have big farm, while it's true that amd is good at zcash not like nvidia though, they are better off mining on ETH + SIA