Because.... Panther primary role is to kill tanks.... and FF primary role is to kill tanks... while Comet is a generalist, like P4.
Panther can damage infantry.
It can't fight any, it contributes, but its not primary damage dealer, because its AT specialist.
StuG with MG upgrade is more comparable to Panther then Comet.
Stats reflect HOW the unit is supposed to engage enemies.
FF destroys tanks by sniping them from long range with low DPS.
Panther destroys tanks by outlasting them and chasing them down.
The sole fact that some people compare comet to a panther is a testament to cluelessness of these people who are utterly ignorant about role of the unit.
Comet is a middle point between med tank and heavy tank, just like panther is in context of TDs.
The comet is the closest analog to the panther in terms of cost and stats. Are you disagreeing with me just to disagree? The only thing comparable between the panther and the firefly is their penetration and main gun aoe. In literally every other category, the panther is FAR closer to the comet than the firefly.
But for the sake of argument let's use their playstyles. The panther is a tank hunter, using its speed range and durability to bully and chase enemy vehicles down. So between the comet and the firefly, which is better at performing in a similar role? Its not the firefly is it. In fact, point to an allied vehicle that can do it better than the comet.
Fool.