Nu-Wool outperforms fiberglass.

What does the U.S. Department of Energy say about air infiltration?

"The most common insulation, fiberglass, does not stop air leakage. In older homes, dirty fiberglass is a telltale sign of air movement (it simply collects dirt like a filter). Certain types of insulation, such as dense-packed cellulose and certain foams, can be effective at reducing air flow as well as heat flow."

Department of Energy bulletin 10099-769