3GB of vram and 6gb of vram, id go for the 6gb as games these days require 3+ vram for ultra and better performance

Other than the VRAM difference, the 1060 3GB has 1152 Cuda Cores as compared to the 6GB variant which has 1280. The 3GB also has 8 less Texture Mapping Units.

On paper theres about a 10% difference in performance between the two cards.

-ozar wrote games these days require 3+ vram for ultra and better performance

What's better than ultra? Also, no, games don't require more than 3GB VRAM. It depends entirely on the game, resolution, and the rest of the system specs.

OP - 3GB GTX 1060 is a cut down version of the 6GB GTX 1060, fewer CUDA cores and obviously half the VRAM. Which one you should go for depends on the rest of your system, your monitor, as well as what you'll use your system for exactly.

1060 6gig is alot better as it gives you room for more settings and has little more cuda cores, well the 3gig model which everyone should stay away from imo due to games depending on how optimized it is would struggle on anything less then 4gigs or if you want to be cheap which you should never cheap out of a gpu unless you dont play games