In my opinion, the clear leaders are the Elves, Dwarves, and Humans (now "Unrelenting Force" gives the entire army a double attack – kudos to the author of this idea :smile02:)
At the bottom of the list is the Academy, because having all the spells gives more freedom of choice and some readiness for various kinds of unexpected enemy skills – having all the spell schools doesn't mean casting them all during a battle, because a hero won't cast more often due to "Arcane Knowledge," and this skill won't give more mana either (that is, the same situation as when pumping all four schools of magic into one hero; in general, pumping more than two schools of magic into one hero is a clear absurdity). In addition, the lack of commander skills won't allow for the use of mass spells, which can often decide the outcome of a battle.
The Orcs also have a quite strong SU; Demons and Necromancers, in my opinion, are a little behind.
Warlocks also cannot boast a strong SU.
Added 4 minutes later
that is, it is necessary to determine whether there are obvious imbalances and restore fairness (as was the case with the Heaven SU)
Блистает там воздушностью прогалин.
Но между кедров, полных тишиной,
Расщелина по склону ниспадала.
О, никогда под бледною луной
Так пышен не был тот уют лесной...