of course, CASTLE!!! - because that's who I play as. Just kidding. They are roughly equal in strength.

Castle - level 1.7 units are the strongest. Only the Halberdier can compete with the Centaur. Champion is in 3rd place, the rest of the units are above average, magic is above average, and the stable is a good helper for scouting.
Necropolis - undead! Level 4.6 units are the strongest, good magic, good ranged attacker, the rest of the units are average. Relatively inexpensive. Also has useful buildings.

65rus, correct the Griffons - they don't have retaliation, they retaliate against everyone, you must have made a mistake.