The latest installment of the Panzer VOR! Series (#6) concentrates on the balance between armor and firepower among the AFVs used by the German army in WWII.
Armored fighting vehicles need to have the proper balance between mobility, armor (protection), and firepower. Increasing or decreasing one would affect the other two. The book has a 3-page introduction on how the different parameters were modified during WWII for the Panzer I, II, III, IV, Panther, and Tiger tanks. It is clearly interesting to observe that with each mark (A,B,C, etc) there was an increase in fire-power and armor at the expense of mobility through the period 1939 to 1945.
The book also briefly covers the same “gun vs armor” equation for the allied forces, including the Sherman, Matilda, and T-34, among others.