If you need 65-70 L, that implies heavier loads. The heavier the load you carry, comfort is more important then pack weight. Exactly how heavy is your load?

I have a 2#12 oz pack that I use for loads under 40 pounds. I am not UL - for a 14 day trip I end up with about 42 pounds. I suffer the first few days because it actually is overloaded for the suspension until I head a couple of days food.

Over 40 pounds (carrying food for others, grandkids gear, or a serious alpine climbing trip) I go to my old Kelty external frame. You can load it up, carry odd-ball sized stuff (like a bear can or climbing rope)and with the extension bar you can distribute the load in many ways. I have redesigned my Kelty and sewed a new bag of lighter material so it weighs 3.5 pounds. I have also used just the frame, and slung a 1 lb Granite Gear pack on as the pack bag.

If the pack weighs over 5 pounds, it probably is made of too heavy material - like others said- may be designed for hunting or other purposes than general backpacking.

The bear can is a HUGE issue with me. Not only is it big and heavy, it is rigid - put in a pack vertical, it ALWAYS makes the pack more uncomfortable - stiffens the back where you want it to contour your back. With the Kelty, I strap the bear can on the top (attached to the extension bar). Also, many packs can accommodate a bear can horizontally only if you are a men's large or x-large. I have not found a single woman's small pack that accommodates a bear can horizontally. A horizontally placed bear can, at the top of the pack, eliminates the stiff as a board feeling on your back.

I suspect that many of us who backpack a lot on trips of varying lengths and varying goals own several packs. Personally, I would invest in at least two packs instead of a one-size-fits-all situations.