Bob, are those ratings the thrust per unit? That's pretty darn impressive if they are! But what sort of watts does the 80mm unit pull to produce that thrust?
Not that it really matters. You're going to have lots of wing area to lift the batteries either way.
I wonder if the sound of the 80mm fans running at a little down from full throttle might also have a nicer sound than the smaller 70's running at full throttle?