Which faction do you like the most?

Definitely Inferno! The units complement each other perfectly; Imps steal mana and give it to the Cave Lords. Just the presence of Hellhounds near an enemy drains and kills them. They are strong in direct confrontations but incapable of underhanded schemes. I only play as them and am deeply upset that the entire Tribes of the East campaign is built on the opposition of all Inferno races. I hope they will be given a chance to redeem themselves.
The first hero should be Grog; he can run across half the map in one turn. If you give him artifacts that match and develop his logistics, he will be able to do everything. If the hero collects all the artifacts of dragon power, an Archdevil will be added every day, and then victory is practically guaranteed.