When discussing the survivability of tanks, the physical size of the tank is of great significance. Especially the profile is important, as especially anti-tank guns would generally attempt to fire against the side of a tank, rather than the front. In addition, the height and firing height of a tank is important, both in terms of target size, and in terms of how well the tank can be concealed in a hull-down position.
Profile Comparison Charts
Height Comparison Charts