I have watched the f-stop's video, as far as the support system it doesn't seem much different than the Trekker 400AW.
As far as carrying gear they all do the job.
The difference is how it feels on your back, and the problem is that it would cost $350 ++ to find out.
I wonder how well it work just buying the internal units from f-stop and then use it with a quality backpack made for backcountry packing