How so? I really know little about the difference between MSIs models, but remember being curious about it at one point.
Manufacturer have multiple models for each GPU. Different cooling system, looks/aesthetics, performance, warranty, noise, etc. Example:
Gigabyte: Windforce < G1 Gaming < AORUS < Xtreme
Armor is the most basic/budget model of MSI. Spending a little more for something better is recommended but overall it should perform well. You could also get the RX 480 if you find a good deal. (580 is 10% faster)
As for which brands are better, they are the same overall. I prefer Gigabyte because I never had problems with it while my friend like the way MSI is pronounced. So it comes down to your preference.
From what I've read the 580 Armors tend to run a little hot/noisy. This can often be improved with undervolting (which is a great way to reduce power/temp/noise with Polaris cards, and is usually a good idea no matter what version you buy), but if you want to overclock at all you may want to get something with a better cooler.
I've had Asus Strix and Gigabyte Aorus versions of the RX 570, and my current Sapphire Nitro+ 580, and from what I remember the Nitro+ runs the coolest/quietest.