The GTX 1060 3GB is a good value option for those gaming at 1080p and right now at $210 it’s also very affordable. Meanwhile the 6GB model is currently retailing for $280 and it's only marginally faster. The reason for this is that the 3GB model is only $10 above MSRP, while the 6GB version is $30 above because it’s a more desirable card for miners and because of the increased memory pricing.
Then we have the RX 580 which should cost $200 for the 4GB version or $230 for the 8GB model. At those prices, we'd pick the RX 580 8GB every day of the week, but sadly right now the asking price for that card is an eye watering $310, writing it off completely.
This might be shocking to some but given the pricing (we hate to overpay) and performance margins, we're going with the GTX 1060 3GB right now.