The Headway MLC (Maximum Legal Carry-on) from Patagonia is a very functional gear bag that works better as a duffel due to it’s uncomfortable (but hideable!) backpack straps.
Other Bags to Check Out:
The GR2 from GoRuck will last your entire life, features a segmented main compartment, is extensible with pouches and accessories and boasts a very rugged, handsome look.
A medium-large sized travel bag with sturdy, rigid outer material, a couple external pockets and a removable internal divider that makes for actually a pretty interesting way of accessing things in transit.
DSPTCH hand-makes bags here in the USA and the Travel Pack is a great example of the kind of extremely durable designs they put together.
The Homebase series from Tortuga features this incredibly lightweight sailcloth material that's water resistant and super strong. (It feels light and scary! But it's damn strong stuff.) This makes for an incredibly light and resilient travel bag.
The Outbreaker backpack from Tortuga is a solid 1-bag travel pick. I personally prefer the less bulky (and more spacious) experience of traveling with the Tortuga Setout, so be sure to check out that bag too. This Outbreaker, however, has quite a bit more padding and protection around the entire bag, so if you know you'll have delicate stuff inside you may prefer this one.