The 3gb are all you need for Zec/Zcl/Zen/Hush.
I am running a small rig with 3 of them right now averaging around 280 Sol/s pulling around 90 W each.
They make $1.91/day each on Zec right now. (The 6gb will only get around 21 Mh/s on Eth $1.61/day)
You will make $15.28 per day on 8x rigs running 1060 3gb and only $9.66/day on 6x 1060 6gb rigs.
If you get the 3Gb over the 6Gb they will ROI 26 days sooner than the 6gb cards if you run Zec.
If your heart is set on mining Eth go with the 1070 or some RX cards.
Thanks for sharing your opinion
As i know 3GB still can mine ETH ( and will be good in next 7-8 months ) but i want to know the difference with 6GB version.
If 3GB can hit 20 Mh it will be good for me Since GTX 1070 is overpriced now ( I mean where i live ) and i can get 8x 1060 3GB instead of 4x GTX 1070 and get more hashrate,also 8x 280 Sol (1060 3GB) Sol will be better than 4x 480 Sol (GTX 1070) in ZEC.