Weighing in rather late, but...Warlords 1 and 2 are cleaner, simpler games than 3. In Warlords 3, the system of combat bonuses and penalties allows you to create stacks that are virtually invincible (with enough time and resources). Something like that could never happen in the earlier games, where the strongest unit is just strength 9 and dies in one hit (instead of strength 15, has four hit points, and uses buffs like lightning or acid).

Money management is also more challenging in Warlords 1 and 2. Unit upkeep is always a problem for me in those games. In Warlords 3, though, I can churn out units like there's no tomorrow and hugely out-produce the AI. That's a slight problem in the earlier games as well, but it becomes quite pronounced in W3.

I enjoy them all, but the series does sorely need a new entry with better AI that produces more units and does better behind-the-lines defense.