I use both--Magic Sizing on light fabrics and starch on all others and have never had a bug problem since MIL moved out. Her junk food attracted bugs. They all seem to have followed her.
I'm not patient enough to use starch on lights so end up scorching it--even the non-scorching type.
Wool is a different story. It will be eaten very quickly if you don't keep up with the moth crystals or cedar shavings.