Considering the croc's health it firing at it with a panther or a pak 40 will have relatively the same effect as a Croc firing and penetrating a Panther.
After a game I had my full health vet0 croc run up against a vet2 stug and the stug killed it. Both penetrated most of the time, but the croc deals very negligible damage to tanks. It also shot the wrong target until I got right up to it. This wasn't an empirical test, but I don't have the time to recreate it in cheat mode. Also, more health means it will take more time to repair when it gets shot a whole bunch, and this too applies to other heavy tanks.