Hi David,
I didn't complete the review of the Jam so I can't comment on that. What I can say is that I found it reasonably comfortable to carry 30 pounds with the Pinnacle (although I typically carry less). The load lifters do make a big difference in transferring weight to the shoulders, making heavier loads more comfortable.
I've never had the issue of the pack collapsing. I use the compression straps to make it as solid as possible when pushing the weight limit.
BTW- this is my winter and mountaineering pack. I use it on every trip in this category. When doing family backpacks, my wife uses her Pinnacle to carry large low-weight loads while I carry our son and high-density gear in the baby backpacking. We both love the Pinnacle.
Best,
Doug