Adams and Mortensen
I remember reading the magazines in which their responses back and forth were printed. The disagreement was a basic one - Adams did not believe in physical manipulation of a negative once it was developed - Mortensen viewed the negative as a canvas on which to add personal art work. Mortensen was a pictorialist only in the fact that his images sometimes depicted scenes from myths and legends.
Mortensen was a Hollywood studio photographer with access to beautiful models and costumes.
Adams was a working photographer whose primary interest was the natural world.
Each was a great photographer in his own right. If one takes the time to carefully read and analyze each of their instructional books they will find the two men used extremely similar approaches to exposure and development. Adams, along with Fred Archer, developed the Zone System, and Mortensen called his approach "The Nine Negatives".
As an aside,the quickest method for determining correct EI and development time for the Zone System in the absence of a densitometer is to use the 9 Negative Test.