When you read more, you'll see that the M4 series had alot of changes through it's life, to cope with changing conditions on the battlefield. It tried several different Powerpack options(like the A57, The Ford GAA, There was a twin GMC 6-71 diesel used in the M4A2, I believe) and the Armament changed as the war progressed. It went from a L/39 75mm to the long 76mm, as well as the 105mm assault variant. But, up till the end, the predominant variant had the short 75.
If this was what was incorporated in the game, Where you could get taken out with a frontal shot at 1500-2000 yrds., and you would have to close to within 500-750 to kill anything else, It would probably wind up a hangar queen. Remember, AH2 does not take maintenance or range into account, and #'s are determined by whoever wishes to spawn it, so those advantages are negated.
Picture this: TT on the Trinity map, you spawn in, you have 8 other M4's there....and you are opposed by at least as many pzIV's, Tigers, T-34's, all superior tanks. You try, and try, and try, but without 30-40 people spawning M4's, you are outclassed. That would be if it is modeled correctly.
This is why you see people asking for the M-26, With it's thicker armor and 90mm gun, would be an even 1-vs-1 match. Now, I could see some use for the over-turret rockets, or the 105mm Howitzer equipped varriants, would be handy knocking down a field town, or FH's or VH's, It would probably become a favorite in that context. My .02$
-Frode