obviously the larger tank but that has nothing to do with the pressure observed at the bottom of the tanks. accelerate both tanks at 2G and the pressure measured at the bottom of both tanks will be 25.98 pounds. what's being discussed is the increased load on the discharge of the pump due to line diameter and acceleration. the diameter has NO effect the length, rate of acceleration and fluid properties does. trust me it doesn't matter if the line is 5/16" or 2" the pressure change at the pump discharge due to acceleration will be the same.