I’ve had a Red Oxx Aviator bag for a few years now. I have both the small and extra-small varieties. These bags are as plain as can be; no shoulder strap, no pockets, no lining of any kind, just tough-as-nails canvas, a good zipper, and strong handles.
My small bag has seen duty as a camping duffle getting kicked around in the dirt, as well as a carry-on for a week-long trip to Italy where it held its own, both as a carry-on (the small bag is almost the maximum legal carry-on size) and as checked luggage. These days I keep a sleeping bag and camp pillow in the extra small (!) and throw it in the car when I know I’ll end up sleeping outside or on someone’s floor. The bags zip all the way open allowing you to pack them sideways, like a suitcase, which is nice for laying out clothes and shoes. The zippers on these bags are nice, smooth, and non-catching; which is essential for stuffing my sleeping bag. The bags are guaranteed for life, and it is easy to see why; they are simple and well-done.
There are times I prefer traditional luggage but it is becoming more seldom. The aviator bags, make no mistake, are completely bare bones. This is what I like about them, but packing for a long trip might require you use some other bags inside to keep things apart. I typically use a small drawstring bag for a pair of shoes and stow an empty reusable shopping bag for dirty clothes. Some people use packing cubes. If you want compartments, a frame, straps, compression, organization, etc. built-in this isn’t the bag for you. Red Oxx makes well-reviewed complete bags but I have really come to prefer the aviator bags for their simplicity.
For the money, I can’t imagine a bag I’d rather use for stowing gear or packing on trips. I have some nicer luggage, but I end up using these bags more often and when I have any concern about durability.