The first thing I look for in a pack is how it carries the load and interfaces with the body, because the point of a pack is to move stuff from point A to B in as comfortable and safe a manner as it can. It needs the right suspension components to do both. A pack that is meant for light loads can get away with a bit lighter components, but not by much. That means it needs something to support the load (most of our packs use at least a frame sheet and then start adding stays as the intended usage weight increases), something to control the load and hold it tight to the support system (good compression), and finally a good method to attach the load to my body as close to my center of gravity as possible. It also needs to be designed in a way that I can adjust all of the to body attachment points and suspension points so they fit my body. From there I want something that is going to be as durable as possible and last as long as possible within reason. What I mean by that is there is a point of diminishing returns where you are just adding weight for weights sake. Some folks would argue that using 500d cordura like we do and a frame sheet with stays is past that point. My counter is that I spend most of my time off trail, and my backgrounds includes time spent living rough for months at a time, so my reference for durability is a bit different than some folks. I am also not willing to cut weight by sacrificing load support and management because I don't want to be fighting the weight on my back. I want it as comfortable as possible.
I think you are using "canvas" as a generic term, and not because you think that we use canvas. Most of our packs are 500d cordura, because we have found it was the right balance of durability, weight savings, compressability, and cost. Sure we could save a few ounces, and that is literally all it would be, by going to one of the fancier materials, but in each case the sacrifices in one of those areas is not worth the trade off. The place that most packs that are lighter truly cut weight is in sacrificing suspension and thus load carriage, which is just silly to me. A well supported and compressed load will subjectively feel lighter than it is, and will stay insync with my body better.
The whole sweat thing just doesn't make sense to me. If I am wearing a pack and moving I am going to be sweating. In the summer if I am moving quick enough, even without a pack, I am going to be sweating. I just expect it. I also don't sweat any less with different pack materials, so again, it is a bit of a red herring. There are packs that include designs to keep the pack away from your back, but all of the methods I have seen place the load further away from your center of gravity, which is going to make the load fell heavier as it now has more leverage.
I am biased, but I think we make the most comfortable packs on the market. I also think our modular design also shines because it allows you to tailor the setup to your needs. I will say that both of these come at the expense of having to take a bit more time to dial in the fit to your body and make sure you are controlling the load.
Co-Owner Hill People Gear
"If anything goes wrong it will be a fight to the end, if your training is good enough, survival is there; if not nature claims its foreit." - Dougal Haston