I will toss in an observation, but first I confess I am a bit of an MR fan boy going back to the Dana designs days in the mid 90s and currently own six of their packs. I owned and sold a tactiplane that is very similar to the 6500 and can’t bring myself to sell a wolf pack alpha which is a modular pack that can be set up like the 6500...so on to my $0.02...
First, a heavier, stouter frame can carry better - more stability and load control - than a lighter frame. It should also, be more durable on average as well. There is a sweet spot where this is very true and especially so when you are talking about heavy loads like packing out meat which can be +60#s easily. However, starting with an empty pack that weighs 8-10# and then adding your load is inarguably going to add to the total carry weight and fatigue, so the real question - beyond the dollar cost - is does the extra weight justify itself in terms of enhancing the load carriage or durability of the pack?
The 6500 is a great pack. In many ways it is an evolution of the old Dana designs terraplane that was one of the most highly regarded backpacking rigs on the market for years and still has a robust following. The 6500 takes that basic design and upscales and weaponizes it for .mil use as a long range pack. It is overbuilt for sure and can haul soul crushing loads like ammo cans and mortar rounds in addition to +100L of gear with no problem. It will last forever under normal use conditions due to its materials and construction.
Having said that, staying with MR, a marshal or a beartooth will cut that 10# pack of the 6500 weight to 7#. A Metcalf (my current favorite) drops it to 6# and would carry a heavy load 80-100# just as well in my experience. You may give up a little bit of durability for the lighter materials but should still get years of normal hunting use from the pack.
There are so options below the 6# mark but IMO but the you start to give up some load hauling capability below that.
So is it worth it? If you carry it a lot and have the $$$, I say yes. You can get a pack that will perform just as well for less than 2/3 the weight. Probably a +10% savings on your base weight (without food or water), which is huge.
Last quick thought, I just wrapped up a 5-day grande canyon backpacking trip with my Metcalf. The other two guys had ultralight packs - a hyperlitemountain gear and a granite gear pack, each weighing about 2#. Going in with food for 5 days and some water, their ultralight packs were at or above their max loads rating and they sucked for stability and load control. Lots of complaints the whole hike in. Hiking out their packs were light as can be and they were a lot happier than me. That experience hasn’t turned me off my Metcalf but it makes me question if it is the right answer to all my hunting and backpacking problems.
