IMO it depends of the shifter levers, old ergo campy at the back for the derailleurs. I have a carbon handlebar with internal routing under the handlebar and works fine. With the new campy ergo from what I have seen people is routing the derailleurs at the front and then under the handlebar, if you use the split going to the back looks like you have more chances to get friction problems but pretty much all of that is debatable. With shimano no clue im not a shimano guy.