In which city is the alt upgrade more balanced?

That is, 50 wyverns will inflict poison damage of 250 units over three turns... totaling 750. In principle, that's not bad; you could also use dark wyverns, but only when there are many of them. Because with large armies, there won't be time to eat corpses; you'll need to attack quickly, and poison will be useful. And in the beginning, paoka will do.