Pixie from Punished Brats had some pixielicious comments on this always titillating topic:
I have some cute and some pretty thongs too that I’ll wear on occasion, but for the most part I prefer bikini cut panties. Also, when doing a spanking scene, we ask that the models wear panties rather than thongs so that it makes sense to take them down. With a thong there really is no reason to take them down as they aren’t covering the target area, but if you don’t take them down, it’s not a true bare bottom, right? So we make it easy and stick to bottom-covering panties that can then be pulled down to reveal the spankable buns underneath. It can be like unwrapping a birthday present.