no offense but this is one of those questions that has been asked a million times. I think I might have asked it too 🙂
I can say that it is all up to preference. When choosing pairs that you want to sell, just buy what makes you feel sexy or cute or comfy, whatever. Also, try to have a bit of everything. I have the basic three: thong, brief and boyshort. Although, I really love going to girls sites and seeing the french cut. Damn those are sexy, no matter who is wearing them. 😛
I personally like anything that has something unique. a cutout or ribbons or mesh. OH, mesh! Thats another big turnon. especially when the girl has a landing strip and you can see right through the panties.
Geez, maybe I should start buying instead of just oogling pictures. hahaha.