Well, I think it's a toss up. Both kinds of backings from 50 years ago and older have held up well considering the manufacturing processes were not so refined as they are today. It all depends on how a quilt is taken care of to prevent fading/fold lines etc. Muslin will show stains more than a print, but will age into a softness while prints may fade. Long term durability might not be known for years to come. I've used prints that have begun to fade already even after a couple of years.