Well, I did sit through the entire video. Nothing better to do on a Sunday morning.
Actually, that's not quite correct, I was looking for ways to put off getting off my butt and getting to the projects I should be working on.
Anyway, My own preference is for external cables, but one of my reasons wasn't even addressed in the video.
External cables enable one to give the shift cables a good firm stretching to firmly seat the housings in the stops, and helps to keep them in adjustment for a longer period after new assembly, or cable replacement.
I have lots of experience stringing internal cable, both with and without full length housings, and yeah, they are a time consuming PITA.(Tri bikes have to be the worst)
But for many that can leave the assembly and servicing in someone else's hands, aesthetics trumps serviceability.