3GB version is not recommended at all. A 970 is faster than it in most situations. This video gives more information on this subject.
Personally I'd skip the 1060 altogether and get a 4GB/8GB RX 480 instead.
Going by that video and also all 3rd party benchmarks, the GTX1060 6GB performs better than the RX480 8GB (except for in Hitman and DX:MD).
Time will tell how each performs in DX12 however.
Imo, GTX970/980 owners should skip the Pascals entirely unless they are getting a GTX1080 or above. I don't think even the GTX1070 is a worthy upgrade from a GTX970/980 as the extra investment is sky-high.
(Sell existing GTX970/980 for 15k, add yet another 25k, and buy a GTX1070. Only the uber rich can justify something like that for 20 more fps heh).
But for those with 2 generation or older GPUS, the GTX1060 6GB is a solid budget purchase.
And strangely even the GTX1070 is a great prospect for this group of buyers as the 'go-for-broke' point kicks in.
The dawn of the 4K era is great for the budget gamer. GPU manufactuers are focussing on being powerful enough to push 4K, then the same die gets chopped up and sold as budget variants, which means great performance at 1080p for the 'poor' gamer even if they buy the lowest of the low junk.
PS: I am speaking for the Indian market where prices are retarded. When buying in the US, the GTX1070 is far far more bang for buck.