Tactical techniques for conducting battles in Heroes of Might and Magic II.

Spirits are definitely stronger overall, in every aspect.
However, sometimes it's not very rational to build them, because you don't need a nest to build Titans.

Then, who should be used in battles? IMO, these are the most important troops at the beginning of the game. After all, building Titans requires a lot of money and crystals. And until Titans appear, Spirits become one of the main stacks... Or am I missing something?