A repost, with some additions:
Tanks of similar price generally have similar ap+av. For mediums, whether AP-weighted or AV-weighted is better is a preference thing. AP keeps the tank useful if more expensive enemy stuff shows up. AV on the other hand makes your light/medium a lot more versatile – it’s easier to provide fire support if you can survive an ATGM shot and you can fight infantry toe-to-toe despite good RPGs.
Wargame vets will remember how cheap high-AV units are capable of steamrolling infantry in their own forests – eugen have slipped up more than once by making and then having to nerf vehicles with a bit too much AV for the price. For the other extreme, Razzmann has demonstrated the ability of cheap high-AP tanks to dominate heavies as long as one can force the fights to happen up close, and prevent the heavy from retreating for repairs after snagging a kill.
For heavies however, AP-weighted tanks have almost no advantages on AV-weighted tanks. AV is useful against all non-tank threats, it lets you fight infantry, push with less risk, rarely even resist an AT plane. AP-weighted tanks on the other hand buck the price hierarchy, but for heavies this is a bad thing. Having AP over AV means your tank can harm more expensive tanks but can also be harmed by cheaper stuff; it’s a good trait for a 60pt medium since you’re usually not worried about 40pt tanks, but a heavy making this tradeoff is just making itself weaker to the cheap tanks you’re usually buying it to counter.
A heavy with an armor emphasis is superior to one with an AP emphasis provided everything else is the same. Having an AP-emphasis around and after the 100pt price mark is a downgrade, not a sidegrade, to being balanced or having an AV-emphasis.