The shoulder straps are oversized compared to the smaller container.  This to better disperse the stress across a wider section of the shoulder making it less damaging to the surrounding soft tissue.  (It's THE reason for the military going to load bearing vests as opposed to the old school harnesses.  You can read more about an ongoing clinical study here;

http://clinicaltrials.gov/ct2/show/NCT01066975   )

With the Daypack Duffel,  the gear is kept high and closer to the body giving the user better balance and mobility.  Different than the average pack, you'll notice the advantages as soon as you start moving with it under load.