I'm talking operationally. I believe the average engagement range in NW Europe was under 600m and the bocage area of France would have seen even shorter ranges. Furthermore they would have allowed situations where flank shots were likely. In these situations the 75 is adequate to take out a Tiger. As for more limited numbers if you gave the Germans M4s and the allies Tigers I would expect the Germans to have significantly more tanks and the allies significantly less. While the allies are still likely to win the breakout is very likely to be delayed and the Germans indeed may be able to make a fighting withdrawl across most of France.