woah I didn't quite expect a heated debate on my pretty boring post.
anyways, after much deliberation, I've decided to go with the RX580. it seems most of you guys would prefer FreeSync over a 30$ savings.
I'm also leaning towards the XFX over the MSI. Now I just need to confirm that it will fit on either of my cases (SG13, and later, the ML08). It's really weird that I can't find this informaton on the specs page of xfx.