A bunch better. I just did mine and if the basement door is shut, you can't hear whats going on upstairs if your down or downstairs if your up.Roxul might be around $100 more than fiberglass. Is it that much better at sound blocking?
I was very impressed with the sound deadening of Roxul.
I found Roxul user friendly too. Cut it with a regular steak knife or butcher knife. Doesn't make you itch either.