Ours' operates about the same. Never noticed any difference. A degree or two wouldn't matter anyway. Either way, food stays frozen in the freezer and we never had any spoilage in the refer section. A small fan blowing on the cooling fins really helps to distribute the cool air evenly throughout the frig.
Of the 4 rigs I've had propane is much quicker to cool the fridge. When it's really hot like it gets here in Phoenix I don't even bother with AC as the temp will slowly creep up. In outside temps under 90 it stays about the same with propane or AC.
Mine seems to operate the same in either mode. A refrigerator thermometer consistently indicates about 34 degrees F. in the fresh food section. Furthermore it cools down in just a few hours from an ambient start.