Distinctly depends on your playstyle. In the current state of the game heavy armor is king, in most situations.

Medium armor is mostly only useful for gank builds, stamina utility builds, group builds or roll dodge builds.

Now if you want to stand toe-to-toe with someone, or fight outnumbered, you're going to have a lot of issues in medium armor. Unless you're fighting potatoes, which is mostly what you see in all those "1337 h4x 1vTrillion 360 no scope" videos.