I would guess that the straps on the Aeronaut are much nicer than the ones on the Sky Train. I packed up the Aeronaut today and wore it as a backback, it was very comfortable. The straps are also very easy to adjust as well.
I got the Aeronaut without the waist strap and don't find it to be a problem.
Oh, yeah, and the Aeronaut holds a ton of stuff.