I get your point about better scenery , more interesting stuff on the C&O. ( although the Youghiogheny River views are nice on the Gap).
The road surface on the C&O for the most part is not an issue with the right tires. However with rain it can be an extremely muddy slog, and the several areas that wash out repeatedly can be unrideable.
Personally, if I was picking one it would be the GAP, but the 2 together make a great through trip.
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You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.