In Oz we pay $278 for a 1060 6GB or $203 for a 1060 3GB
which would you go for in an 8-10 card rig?
it depends what your goals are, I don't think you could really go wrong with either and those aren't bad prices all things considered
personally i'd try to build both eventually xD
The DAG file for ETH will exceed 3gb on 04/MAY/2019, it wont exceed 6gb until 03/OCT/2024. so 3gb cards will be no good for ETH in 1.5yrs but 6gb cards will be good for 7 years. It is worth the ~50-75$ per card (if you have the money for that) to buy 6gbs and get the extra 5.5 years of possible productivity