Good examples are: Mirella Freni, Ghena Dimitrova, Elena Obratzsova, Elena Souliotis.

Bad examples are: Maria Agresta, Anja Harteros, Elina Garanca, and Renata Scotto

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 or throaty singing, or some combination of both.