Choosing between RX 580 vs GTX 1060 6GB with a FreeSync Monitor

gonzaddr

Prominent
Sep 15, 2017
2
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510
Hello. I recently bought this PC:
G4560
Gigabyte GA-B250M-DS3H
G.Skill DDR4 8GB 2400Mhz Aegis
XFX 600W XT Full Wired 80+ Bronze

And I have a full hd monitor with FreeSync (Samsung F390). It's new, so I will use it for years

The thing is, I'm between this graphics cards:

Gigabyte Radeon RX 580 Gaming 4G u$s 370 (https://www.gigabyte.com/Graphics-Card/GV-RX580GAMING-4GD-rev-10-11)
EVGA GTX 1060 6GB GAMING u$s 375 (https://www.evga.com/products/product.aspx?pn=06G-P4-5161-KR)

Both cards cost the same in my country. I can't buy the RX 580 8gb model, because it cost twice the price of the 4gb model.

I've read that 6gb will help more than 4gb, but since I've have a FreeSync monitor, well... I don't know.

So, please, can you help with this? Thanks! :)