It seems like they did similar if not the same experiments and that 731's information was more valued. Also, did 731's information give way to any pertinent medical knowledge?
We had a huge unresolved source debate here a month ago on the subject.
It's still in the air whether 731 did good science and whether they gained any useful medical knowledge (I'm in the yes camp)
But what's clear is 731 focused heavily on biological weapons research (that's what the unit was for) where as the Nazi used medical research as an excuse to butcher people.