A hairbrush to a fully covered bottom, or a healthy bite to the inner thigh? 
Having experienced neither I am going to think that the inner thigh is going to suck like a mother trucker. In one of my first jobs working with people with learning difficulties I was bitten on the thumb and also the inner forearm, and let me tell you, that inner forearm bite was no joke, especially when you are trying to get a clean release as opposed to a Walking Dead style mouth withdrawal, lol. The rulebook says to push your arm into the mouth and then pinch the nose to cut off breathing to get a release, the book neglects to tell you how much that mother is going to hurt.
Another thing of note, could the artist have drawn the grown woman any smaller?
Anyway, hairbrush over the skirt and panties or bite to the inner thigh, which one are you choosing as to which hurts more?
