Any blown materials will settle at first. I personally have found blown fiberglas to be more susceptable to settling, simply because it's mostly air. The "Perception" of settling is partailly because we tend to think of insulation in terms of inches, not taking into consideration the R per inch differences. the result is if we think of R-38 as 12", we look at cellulose that produces R-38 with 10" and think it must have settled. We look at Blown fiberglass that may have settled an inch & is still 15" & think we're doing great.
The ONLY advatage that fiberglass has over cellulose is weight, an that only is an issue in extreme cased.