Got thinking about this today as I was re-evaluating my current inventory of packs. I see that there are a few commercial external-frame packs sill available, as well as milsurp. Is this design outdated? Has the internal frame taken over when it comes to packing big loads?
The best suspension systems are found on internal frames. The only packs I now haul on my back are Osprey.
For general camping, hiking, or rock scrambling I think most would agree. However, try to stuff a bull elk quarter into- or lash it to- your internal frame pack and the versatility and utility of a good external frame pack becomes apparent.
Couple of thoughts...
First, big loads suck. They just totally, totally, totally suck. They wreck your knees and compress the discs in your back, which is a lousy surprise in your 50s. If there is any way to avoid big loads, do that first, imo.
Second, there are places where big loads can't be gotten rid of. Winter camping is one. I guess some forms of hunting demand it, but to be honest, I suspect this hunting pack thing is more of a western state issue. Nobody I know in the east is dragging out deer or moose on a backpack. Regardless.... the basic trade-off is between greater flexiblity and closer to the body carry (internals) and better "on the hips" carry of heavy loads in an upright position (externals). For backcountry skiing, I prefer my internal. For trail hiking, my external. It's worth noting that the AMC hut crews tend to use old-style pack frames for carrying soul and spine crushing loads up and down from the huts in New Hampshire and for good reason.
Three, I think Leghog is mostly right that many modern internal makers (Osperey, Gregory) have better should straps and hip belts, but I wouldn't rule out external/hybrid makers like Mystery Ranch. But on the other hand, I don't think suspension is everything. To my chagrin and happy surprise, the old Kelty Tioga I purchased used carries incredibly well, despite it's crude suspension components. A bit part of this is how incredibly well it transfers weight to the hips and how the rigid pack frame entirely eliminates sag in the system as mile stack on top of miles.
For really light loads, I like a frameless internal. But for moderate/heavy loads I go with my Kelty now, unless I'm skiing. But we'll see. I may try the Kelty for skiing this winter.
Kelty Tioga by
Pinnah, on Flickr
Note, Kelty sells new hip straps and shoulder straps on their web site so if you can find an old Kelty for cheap, you can easily upgrade the suspension. The new hip strap is not reienforced but is quite comfortable for loads up to 40 lbs.
