You probably already know this but the ap round is a skill shot, you more than likely miss the panther due to its speed.
Also, you get a cue if the player is firing a skill shot because the turret won't track and lock in place (goes through objects, best used when not in sight).
In turns of vet, the panther would have a huge mobility advantage thanks to blitz (and slight armor) over the pershing while the pershing would have accuracy.
I am talking about the M36 "T30E16 HVAP-T Armor Piercing Rounds" not the Pershing's "Fire M93 HVAP Armor Piercing Round".