Do the panels insulate better than stud walls filled with fiberglass batts?

Yes. When evaluating the insulating performance of a wall system, several factors should be considered. Most common among these is "R-value." R-value is the measurement of the ability of different materials to resist conductive heat transfer (movement of heat through solid material). The higher the R-value of an insulating material, the better it is able to resist heat loss or gain.