The M4A3W 76mm and the Pzr IV are very similar in all attributes but one: rate of fire. The rate of fire and the effectiveness of the 76mm AP round from the M1A1 cannon will win vs the Pzr 75mm KwK40 L/48 in a shot-swap battle. The M4A3W 76mm has a %33 faster rate of fire (M4 = 3.6 seconds, Pzr IV = 5.4 seconds). The penetration abilities of each round are too similar to give either one a definitive advantage, likewise the armor of each is close enough to put them in the "equal" category.
The rate of fire is far more important than most people realize, imo. If people take into consideration it take a 3 shot volley, typically, to range and connect exactly where you want the shot to go, just how fast can a Tiger, or Firefly, or T34/85mm do the trick? The M4A3 variants can do 3 shots in just under 11 seconds. The T34/85mm does 3 shots in 20+ seconds. The Tiger does 3 shots in just under 19 seconds.