Well, even if the model is an attractive lady, drawing what is there, rather than what is in your brain can be tricky. My opinion is that you should generally use models that are closer to the ideal, not grossly overweight or unattractive ones. Getting a likeness isn't easier with the body than the face, I don't think.
Sometimes it can be easier to draw the heavy ones, since the actual structure is hidden. Plus, somehow there is more at stake in getting the attractive ones right, so one tends to be less relaxed, which is a hindrance.
What is truly odd is that even though the model is attractive, when you're trying to draw her (or in the case of female artists, draw him) your mind isn't focused on anything other than "I hope I get this right."