Quote Originally Posted by Neale View Post
I would tend to go Ethernet to give the best chance of not having to diagnose them in the first place!
Absolutely. I value my time more than wasted hours debugging an unreliable system. I have experienced unreliable operation over USB on a RepRap 3D printer. For the mill I got a cheap ethernet motion controller; I have, this week, taken delivery of a UC300ETH. For me, ethernet all the way.