4000 cubic inches is 65L, so I have a Sea to Summit Hydraulic 65L that fits your minimum size requirement.
My pros and cons will be different than yours. Unlike most packs, it is water proof all by itself. I have used it packed to float in the river, just swimming along while it floated. It has mounts that are convenient to attach an external molle panel to, and when I was using it as my main pack, I had it set up to accept a machete, the silky saw, and if I so desired, a scabbard for the AR. The shoulder straps are made in a such a way that you can attach flashlight or multitool holders. I never had a problem with it, it came from the factory adjusted to fit me, just by chance. I was happy with it. The various buckles are plastic, but the shoulder straps and waist belt attach with red aluminum webbing hooks, and would vary rarely come off the main pack when I set it down. It is obviously just one main compartment, which is what I like. I make smaller dry bags for all my gear, then label them, and I don't really have a problem finding anything inside the pack. The problem for me was size. After using it for two years, the longest trip it was on was a week, it started feeling small for my needs.
I consider it a good choice if you are on the water a lot, and don't need to carry everything in one pack, and don't mind making or buying a molle panel to expand it a bit.
I replaced it with the Seal Line Propack, which is a 7000 cubic inch pack, I can literally set it down and get in it. It is an internal frame pack, but the internal frame is just a sheet of plastic, and will flex if you stuff the pack full, but so far hasn't been a problem. I had to take out the internal frame sheet, and trim it to make it possible to adjust the shoulder straps to my torso length. It is much more difficult to add an external molle panel too, because of its design, but I did and I'm pretty happy with the result. It is huge, and with all my base gear, and food and water, there is still room left over, even more so with the machete and saw and water mounted on the outside. If I wanted to add the rifle scabbard, I would need to add some mounting points to the bag, I will be doing this soon. Once it is adjusted it feels great. You can replace the plastic waist buckle with a Cobra Dring (I did) and the waist belt itself seems to be easy to put a pistol holster on, as long as it has a clip, not a holster that you need to run a belt through. I can just get to camp, dump it, and use it collect firewood and water, or grass or bedding. It easy to clean. To me it seems a lot more multi purpose than a pack with a lot of zippers and compartments. I think it was $150?
Either way, I wouldn't go back to a non waterproof pack. Some of the places I camp are on islands, and I can get dropped of at the road, and walk out to the river, and swim right over no problems, no changes or separate bags to put my pack in. Rain is never an issue. The Propack is meant to be a Portaging pack, so big loads, but for a short distance. But I use it as a hiking pack.
I haven't owned a pack as nice as an Eberlestock. So I can't speak on that.