u ignore ant positive thing about the FF (u still have to count he 45 mid range) and most engagement dont happen in 60 range and as i said the FF has actual medium tank armor so a medium tank can't just kill it from the front like a su 85
FF has worst penetration of SU85 and Jackson, especially with vet. It also has the worst mobility, it cant chase retreating tanks unlike Jacksons. It costs way more than and other medium TD and you will have to burn 100s of munis to make it somewhat effective. The only thing the FF has going for it is it´s accuracy. The fact that it has a turret makes very little diffrence considering the rotation speed is lower than the turn speed of other medium casemate TDs.
it's the only tanks that with vet needs 1 less shoot to kill a medium tank, i take that over pen any day as pen is chance based damage is not ( and yes 1 lees shoot for panther and heavy tank too)
even if 1 shoot doesn't pen it would still take only 4 like any other tank but the difference in pen is not that big (as most armor have been nerfed)