I like cavalry, massive hits/gold ratio, at least sometimes. Even if your unit is often decimated soon after. SF as close second, because it's just cool to show off with a 1500CS+ unit
also, I've had some great regeneration rates: 70 men unit, 69 wounded one dead, all but a few recovered in 2-3-4 turns. Never used MI or ranged SF. Every now and then I get large archer/infantry units, for TOs or sieges