There's no downside as far as I can tell and it certainly adds to the visual appeal. There are pics on the Internet of Piolets with 29x3 Plus sized tires. Single chainring only if you run 29x3 tires.
re that mono-stay setup, I know I don't have the frame knowledge, but does anyone know if there is any downside to this setup of the seatstays?
I imagine this design helps with getting really wide tires on it, which along with the Troll, can certainly open up pure off road possibilities if you want to go that route.
what about horizontal vs vertical dropouts? I have bikes with both and really never had thought about them, especially not in terms of what was better, they were just "there" and worked when I took a wheel off and put it back on.
re aesthetics, I think both frames are neat looking, especially the small details on both as well as the diff shapes and curves of each.