Not to discourage further responses, but I answered a similar question some time ago here. Major General Alvan C. Gillem, the head of the Armored Command, penned a letter to the headquarters of the Army Ground Forces on 1 September 1943 noting the merits and demerits of the 75 mm and 76 mm guns, and clarifying his position on the matter in response to a 21 August 1943 letter originating from his headquarters during his absence on a fact-finding mission to the Mediterranean that had essentially stated the exact opposite; Gillem was against a complete switchover in production to the latter, due to the need for tanks to cooperate with infantry and fire effective high explosive shells.

The 76mm Gun M1 as a tank weapon has only one superior characteristic to the 75mm Tank Gun M3...armored penetrating power. The 76mm gun will penetrate on average one inch more armor than the 75mm tank gun M3 at the same range. The high explosive pitching power of the 76mm gun is inferior to that of the 75mm gun. The 76mm HE shell weighs 12.37lbs and has a charge of .86lbs explosive. The 75mm shell weighs 14.6lbs and has a charge of 1.47lbs of explosive. The exterior ballistics generally of the 76mm gun are less satisfactory for a general purpose medium tank weapon than the 75mm gun. The 76mm gun has an extremely heavy muzzle blast, such that the rate of fire when the ground is dry is controlled by the muzzle blast dust cloud. Under many conditions this dust cloud does not clear for some eight to thirty seconds. The presence of this heavy muzzle blast makes sensing the round extremely difficult for the tank commander and gunner.