I purchase more from HSN than I do from QVC. (this was not always the case) I've always thought QVC models were far more professional than HSN models. HSN models always struck as dual employees. Sometimes they answer phones; sometimes they model clothes.
QVC booked (I do not know if they still do) their models through a modeling agency. I have a relative who was a popular model back in the late 1990's and early 2000's. She did commercials as well a print adds for major department stores.
edit
There is a very nice article in the June Insider about Jacqui, the model.