Your first faction.

Some prefer to play as all factions because each has its advantages and disadvantages:) And I am one of those people.

I also choose depending on the opponent... But most often I play with my favorites... in Heroes of Might and Magic III, it was Inferno (when I played it for the first time)... then always Dungeon (because of my favorite ranged units), in Heroes of Might and Magic IV, of course, it was Chaos (although I also loved Cyclops), and in Heroes of Might and Magic V, it was Warlock (probably because of the witches)...