If you are wanting a dry duffel specifically, have you looked into Watershed duffel bags? They make the best dry bags Iíve ever used, very bomber, completely dry, trust them more than any of the others Iíve used. Iím not crazy about duffel designs in general, so I opted for one of their backpack style bags years ago and love it, but I have used their smaller duffels in the past as well. I know two professional photographers who used them for their cameras while whitewater kayaking, both felt they were just as confident in keeping their cameras dry in the Watershed bags as they were in Pelican cases. Thatís saying a lot. While they arenít cheap, they are priced a bit lower than Yetiís. Iíve not used a Yeti Panga, but judging from their coolers I would expect they are probably top notch too. Just expensive!
If you donít need a completely waterproof bag, Iíd agree with recommendations for Patagoniaís Black Hole. Great bags, have had two different ones, hard to upgrade to one with wheels for airport travel.