Appearance/discussion of Academy units.

I think it's easier to build in the Academy. Upgrading is certainly harder, but still. And in general, it's difficult to assess the usefulness of level 7 monsters, as they appear very late in the game, even on Veteran difficulty, and their numbers are small, so it's not yet entirely clear how much effort should be put into building them. Perhaps it's more beneficial to make a couple of extra upgrades to the troops you already have.
P.S. I'm talking not about the campaign, but about hotseat or online play.