Biggest difference to the pilot is that your relatively blind on the inside while turning in a high wing.
Low wing you get a much better view of the circuit when your going round it.
Highwing gives a better view looking straight down which some people say makes nav easier.
Personally it dosn't bother me either way if its a high wing or low wing configuration.
Must be a bit crap in a bi-plane you get the worst of both worlds.
MJ