In years of teaching a drop I find that some can pitch a peel better than a roll over and vise versa. I truly believe that it is really the individual's ability to throw either pitch rather than the pitch. A pitching coach should be able to teach both and find out which one is better for the student to throw rather than say here is how to pitch a peel and not be willing to teach the other when it is shown they do not perform well with the peel.