In which city is the alt upgrade more balanced?

The Dwarves have a fairly balanced roster. It might even be the most balanced. The choice often depends on the player's chosen tactics, rather than one upgrade being inherently stronger than another.

I agree. The Dwarves have the most balanced roster, although it's not perfect. For example, players almost always choose electric Trolls, and I don't know of any cases where fire Trolls would be better.