Note: I have both; the Aeronaut I purchased used (from a forum user), the Tri-Star I bought new.
If I could truly keep only one, it would probably be the Tri-Star, but if I could order a bag to spec, if might be an Aeronaut with some Tri-Star features (more flexible outside pockets) and closer to the Tri-Star's size, but with less interior organization.
Went on a 3-day trip recently, had both to hand, chose to travel with the Tri-Star because of the slightly smaller size. Either one was more space than I truly needed, which (in that case) was actually a plus for the interior pockets of the Tri-Star -- it doesn't get floppy when underfilled. The downside to the interior divisions to me is mostly weight -- the Tri-Star is way lighter than an equivalent hard-side, Yes, but the heavy-duty dividers do add ounces.
It's a hard choice, though -- which is why I see that the original poster, and so many commenters have taken the same path and bought both