I've done bindings both ways. For wall hangings and miniature quilts, I use the backing-->binding method. With bed size or lap quilts, I use a bias binding. To be honest, I have great difficulty mitering corners, so I like the backing-->binding much better as it is easier for me. (A New Year's resolution for me: learn how to make mitered corners properly!) Either way is acceptable. Remember, there are no quilt police! One caution, however, if you are making charity quilts, make sure they allow non-bias bindings - some groups don't.
Anita