bigger holds less better than less holds more
Chowbisou:
I bought the Aeronaut before the Tristar came out, and may yet buy a Tristar or Western flyer, but if I could only buy one bag, it would be the Aeronaut.
The reason is simple: flexibility. you can always pack less in the Aeronaut, but can't pack more in a smaller bag than it will comfortably hold. This takes discipline, sometimes, but also comes with practice at one-bagging.
On the other hand, I came to the Aeronaut from both a 2004 Patagonia MLC and a Red-Oxx (custom ordered extra wide). The MLC was a two compartment bag, and was easier to pack clothes in (flat-packing). It took me a while to learn how to pack the Aeronaut well. Now I miss it when my wife insists I take a wheeled bag. I like to pack one end pocket with things I will use on the plane when it is the only bag I take.
But I often take my Imago with it in the cabin. In that case, the Imago carries my laptop and reading materials/headphones. I just bought an 11" MacBook Air which is wonderfully light and compact. Laptops are the big drawback for the Aeronaut: they are hard to get in and out for the security check or when the bag is stowed in the overhead. You can get around this by carrying the laptop in a sleeve with d-rings and a thin shoulder strap, which then can be packed in the Aeronaut for boarding once you are through security.
If you are still undecided rest assured: once you get hooked on Tom Binh bags, you will almost certainly wind up buying another.
bb