All you'll end up compromising is a matched fuse and wings! I looked at it this way:

Ultracote weighs 8.5 gm/sqft. On an 1,110 sq in wing (2,220 sq in of covering), that adds up to 131 grams. I'm through primer on my wings and have added 120g, so while I will end up a couple ounces heavier, I think I'll have a more durable, better looking finish. (That contest balsa dents just looking at it!)

Monokote is lighter, but relaxes and wrinkles over time, so I won't use it anymore.

The other consideration was cost. I figured it would be $100 to cover or $100 to paint. To do a combination of both would be $200 since minimum quantities are enough to do a complete plane. (Granted I wouldn't have to do four colors on the wings, but that would be another compromise!)