A beast that when you face some mbts can have some problems to penetrate. AP is much more reliable even if it does less damage.
I really think that it should shine with Sabrina with all 4 the skills to swap ammo faster selected as well the crew one. In PvE i feel much more confident to load mainly HEAT, against human players sometimes i chose to go for the safer, even if less damaging AP.
With Sabrina's 4 skills and the crew's one stacked you cut more then 50% of the swapping time and is possible to react fast to the situation having the proper ammo loaded in the rack, if also the minimap is used. But I have an other build for Sabrina so I am only guessing about it. (EDIT: still when my Sabrina will have enough xp surplus to remain colonel without using gold i am thinking of changing her skills in that direction sacrificing crew damage bonus, as she has already a huge component damage bonus END OF EDIT).
I would not say that loading HEAT is always the better choice, it is my usual one in PvE, if you can not pen frontally that MBT you usually have other objectives to shoot at, and many boots sit still, while good human players always move, so to aim at weak spots from distance is not so easy, but in PvP i had faced a lot of situations where i had HEATH loaded and with some AP shells ready to go i would have been way more effective.