Since I make my own 'spray startch' from the gallon bottleo f liuid staertch (1/4 starch to 3/4 water in a spray bottle), I would vote for startch.
THAT SAID, always always wash oout your quilt after finsihing it. Bugs LOVE both sizing and starch. This is especially important if you give a baby quilt as a gift to a new Mom.
Julie