Good examples are: Rosa Ponselle, Anita Cerquetti, Maria Callas, Irina Arkhipova, Birgit Nilsson, Sylvia Sass, Grace Bumbry, Leyla Gencer, Elena Obratzsova.

Bad examples are: Anna Netrebko, Diana Damrau, Elina Garanca, Christa Ludwig, Marilyn Horne

This is not really about old school vs. new school since some of the "bad" examples are older than/the same age as the "good" examples. It is mainly about open (pharyngeal) singing vs. restricted singing in the mask (Damrau, Horne, Ludwig) or throaty singing (Netrebko, Garanca), or some combination of both.