I bought them for their style, and I found them of amazing quality, thick and susbtantial knit.
My socks (I tried Pantherella, Marcoliani, Falke) never developed holes so I cannot comment about durabilty.
About the lenght question I simply prefer over the calf lenght because on me mid calf length always tend to get down.
Buy two pairs and try them, you won't be dissapointed.
My next purchase will be the cable model.