Story and voice acting.

As I said before, the plot, in my opinion, may not be as good as in Heroes 3 and 4, and most of the Might and Magic games, but it is much better than the nonsense in Heroes 5. That's already a plus.

How interesting! And on Hugolka, a slightly different order is given:

How should the campaign be played? And will the player lose much if they play them in the order they are placed in the game?

In the first post, it has been corrected: the second mission of the Stronghold takes place in parallel with the first mission of the Sanctuary. I don't think the player will lose much in terms of plot perception if they don't play in chronological order (based on references in the plots of some campaigns to events in others, one can get a picture), but it is still more convenient that way.