I'm almost embarrassed to recommend a simple Ogio Sport duffel bag, it was a gift from my department in 1992 but probably would retail for $50-75 today. Mine is a 20 year old duffel that has survived easily over 1 million air travel miles in that time. I generally travel casual but its carried a single suit usually and can handle two suits if necessary. I meet everyone from government bureaucrats to sultans, so occasionally I will shy away from the duffel and carry on a suit carrier too.

Suits in a duffel - you have to know how to pack your suit, but I'll take the Pepsi challenge with my department VP any trip on whose suit looks fresher when we come out for a meeting.

Ogio has changed styles since my vintage 1990 bag, but every zipper and every seam has held up marvelously on personal and business travel. It has a reasonable shoulder strap that I seldom use but keep in a side pocket. Never met an overhead I can't put it in and generally it fits under every seat when required to do so. Expands enough to bring home gifts for my kids, and generally I'll chuck non-privileged collateral I collect on the road into the duffel rather than have it spill out into my laptop bag (which is a Tom Bihn, equally good and recommended). I love the duffel best when I travel light, socks underwear and a change of shirts and pants, then it really shines. My wife tends to snag the duffel now when we go out on vacation somewhere.

YMMV