ORIGINAL: Against the Mk IV, they had an opponent similar to the M4 in armor but with a better gun; the L43 and later L48 were both better guns than the Sherman's early 75mm gun. The M4's gun could knock out a MkIV but the Sherman was vulnerable to the MkIV's gun at longer ranges, so the only real advantages the Sherman had was in mobility and numbers.
I would disagree with the conclusion here. While true that the 75L48 had better armor piercing performance at all comparable ranges versus the 75mm M3 gun, the armor protection on an M4 (especially the wet stowage versions) compared to a late model PZ Mk IV, ensured that both weapons could penetrate their opponents armor at the same range and angle. Both would fail to penetrate the hull front of their opponent at 1000yards & 30degrees - but both would still penetrate their opponents turret front at that range, etc.
Moreover, I can't think of a single significant engagement where M4's were caught and destroyed by Mk IV's - strictly due to the latter being at a range too far for the M4's to return effective fire.... though that was often enough the case with Panthers and Tigers engaging M4's (Operation Goodwood?).
The US Army did better than a sturmgeschutz mod on the M4...they put a fully rotating 90mm gun turret on the M4 and produced the M-36B1 - in time to get to Northern Europe in significant numbers.ORIGINAL:
And the US never had anything like the StuGIII, Hetzer, or other armored assault guns/TDs. Too bad, a turretless 90mm gun mounted on a Sherman chassis with an armored box would have done some serious damage........
Going back to topic, I see no advantage here between a T-34 or an M4.





