My guess is they're the same
I used to hear a fair amount of road noise and thrum through ththe back of the truck, UNTIL that is, I put a heavy weight folded moving blanket on the rear deck floor. It made a big difference. The truck is noisier when the road is very wet. Most of the sound is from the rear, resonating in the cargo area.
I also notice that leaving the privacy curtain oulled over the rear storage area cuts down some noise as well. I read a few posts around about sound proofing the truck, but if I could just do the cargo area, I think it would make a big difference. Also wonder if placing a piece of plexi over the rear seat (like a middle rear window) would also cut down road noise.
Otherwise it is a very quiet vehicle, better than my last Olds sedan in fact.