Not every brand offers an 80k size. And likewise not every brand offers a 90k size. More than likely both are more than adequate for the home, but only a heat loss calculation will tell you with certainty. Also many times 60,80,100,etc. models will be 95% efficient condensing furnaces whereas 70,90,110,etc. models will be 80% standard efficiency models. Post the model numbers you were provided.

Bigger isn't better! If 95%, those 90K models will want to mvoe a lot of air. If ducts don't support it, will be noisy and troublesome.

How big is the house? Where? How well built?

drzzz

what size is your home?

what location?

what size outside condenser are you replacing and what size and efficiency of furnace you are replacing?

baldie is right. bigger is not better.

post back.

IMO