Originally Posted by
tarwheel
I've got two bikes currently with internal routed cables and I've previously owned others. Internal routing is nice because it looks cleaner and the cables don't get in the way if you ever use a car-mounted bike rack to carry your bike. Also, external cable mounts tend to get paint chips that eventually allow rust to form. Many older frames with external mounts have rust around the mounts, if you ever shop for older bikes.
+1
Beyond what you mention, it's a lot easier to clean and wax the frame without the cables getting in the way. It's not something I do often but it's part of my routine to prepare the winter bike for use. Things like frame bags are easier to get on and off if you don't have to feed any straps under cables.
I think being able to do away with these minor inconveniences probably makes up for the challenges of running new cables, -which would only be done once every few years at most.