Cargo vans, pickup trucks, and station wagons. They all haul but in different styles. I've owned and driven each and would be hard pressed to choose which I preferred as each was best suited to different tasks. This is my poor analogy for packs, barrels, and duffle bags.
Packs I find the most comfortable to carry large or small, but unless you use a clamshell opening style backpack you'll face the same chore of packers everywhere. Diving in from the top opening to search for that all elusive whatever. Packing cubes/organizers help solve this.
That's where duffels excel. Full length side opening makes packing/unpacking so easy. Provided the carry straps are sized appropriately the bag can be carried as a backpack. The shoulder strap works as a tump I've found.
For hard sided containers the barrels work very well, but only if you need durable waterproof protection for your contents. Harnesses make them suitable for backpacking over portages though I find them (30L and 60L) less comfortable than soft-sided packs.
This vs that makes for good comparisons for whatever you're doing, wherever, and whenever. All three choices have their own advantages and disadvantages, which might be why I have some of each category. Our small barrel is ideal for food/kitchen. Organizers keep it tidy inside. Our 115L dry pack is great for gear we only unpack once a day, tent, sleeping bags etc. and is very comfortable to wear fully loaded. The canvas packs just feel right and can't be beat. The sizeable duffel (maybe 50Lish) is for all and sundry we may want access to at any given time.
There have been times I've driven the old truck wishing I had my van again, driving my van wishing I had my old pickup, and yes there are times I miss the old wagon. I didn't set out to own packs, duffels and barrels but I'm glad to have the choice. But that doesn't mean you need to park all three in the driveway.