There are.

Performance are similar between the 3 and 6 gig memory, but 6 gig one has a better resale future vulue and won't be affected into next Ethereum dag stuff that will block every gpu under 3, or 4 go of memory.

There is as well the memory manufacturer that you may find while downloading GPU-Z. You want samsung ( Best hashrate and best overclocking abilities )

You don't want the single fan versions of the 1060s, you would lost more than 10% hashrate.

If the 1060 has a 8 pin connectors instead of a 6 pins, it's a must.

Always compare overall Mhz in specs, take the one that has more of those.

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I'm still testing my 4 EVGA 6 go with 9 go of memory clock instead of 6, I found another problem with the power supply I received, too high 12v voltage so it destroye one motherboard, and one of my gpu ( glad EVGA has great customer services, they will send me another after I sent it back )

So far, they are all Samsung memories.

I also recommend the ASUS GeForce GTX 1060 STRIX-GTX1060-6G, best hashrate so far : https://www.newegg.ca/Product/Product.aspx?Item=N82E16814126114&cm_re=1060-_-14-126-114-_-Product

I've ordered 5 of those since they are new since only a few weeks ago. I'll have to test the dual mining to see if the 9 go make a nice difference. If it does, then I would recommend them instead of the ASUS. ( Future Resale value, best hashrate, samsung memory, all what you want heh )

Noticed that a lot of people has MSI as well, can't say much about them though : https://www.newegg.ca/Product/Product.aspx?Item=N82E16814137018&cm_re=1060-_-14-137-018-_-Product

https://www.newegg.ca/Product/Product.aspx?Item=N82E16814487378&cm_re=1060-_-14-487-378-_-Product