disagree with you waystin and smoking the main gun is not hard hitting at all. Its lighter than a panzer h's gun according to the stats. Its armour is very weak etc.
Um, the main gun of the M4/76mm and M18 is on par with the Panzer IV H, and only the Panther, Tiger, Firefly, and King Tiger beat it in AP ability (and now the Jagdpanzer IV L/70 and Jagdpanther). And yes, the T34/85 takes a back seat to the M4/76, M18, Panzer IV F2 and H in terms of AP. The only advantage the M4A3/76mm has over the Panzer IV H is a 5X magnification for the main gun site and "sloped" armor. Otherwise, the H and M4/76 are two peas in a pod for the most part (speed, reload rate, MG's, ammo count, etc). Also, keep in mind that the Panzer IV (F1, F2, and H) all have better HE than the M4/76mm.
FWIW, I prefer the Panzer IV H's tank sight over the M4/76. Yeah, the 5X is nice but the clarity of the German sight is nice and I learned how to dial in the distance using the mili-radian system I can get more first shot hits with the Panzer IV H (and F2).