Think you can use a gtx 1060 3gb and get high 200s. No one wants em cause they wont be good for ethereum in future.
Id price the length you can use a card into your equation tho.
Out of the nvidia tho I like the 1070 cause of versatility.
The 3GB version of the 1060 is fine for Zcash. The 6GB gets marginally better performance on equihash, definitely not enough alone to justify the price difference.
However, the 6GB version is, as you said, more appropriate for mining Ethereum.