For the last ~12 years I've been using the TNF Base Camp Duffel. I have it in three sizes so I always have a reasonable option regardless of the length of my adventure. The Backcountry Trekker just replaced the medium Basecamp as my go-to duffel for most trips! The Trekker meets all of the criteria on the MUST HAVE list for a duffel, including comfortable backpack straps, durable/water resistant material, strong zippers, exterior compression straps and some amount of interior organization pockets. Also, for a mid-size duffel, fitting into an overhead compartment is crucial.
Where the Trekker wins is with the smaller details. To me, the absolutely biggest benefit is the massive, water-resistant internal pocket. I used this duffel on an 8-day trek up Kilimanjaro, and that pocket became my dirty laundry zone. Those of you who have hiked Kili (or done any 8-day trek for that matter) know just how badly you, and your clothing, will stink by day 3. Being able to take off the gross clothing and confidently know I'm not pre-maturely griming up my clean stuff was good peace of mind. As I put dirty clothes in, that pocket seemed to keep getting bigger. By the end of the trip, I ended up having half of my clothing and a pair of muddy trail runners in that pocket. Not only does it keep your clean stuff clean, but then you don't have to go rummaging through a pile of dirty clothes to get the one clean shirt you're looking for after walking for 6 hours. WIN.
The two interior pockets in the lid are also well thought out. The one held a book/journal, with the other having an extra headlamp and batteries.