Heavy cav... Their sword range dominates everything else. Regardless of speed I think 2 cav of equal skill the advantage goes to heavy over hussar just because of the sword range. It even helps out with feinting and attacking ground troops much better. Most lancers are garbage and can easily be blocked, reared, and beaten to a pulp and dragoons are worthless once they shoot and generally miss their target. I won't deny hussar is fun but heavy dominates when anyone with competence uses it.
Cav vs. Cav the heavy is a beast, though generally having a tougher horse helps in mass cav actions anyway so Russian dragoons are not bad at all as well.
When you outplay a heavy, land a big hit over his shoulder, and he lives...then you slash again and he lives...then you circle round the other side, trick him again, hit him and he lives..yeah. Healthy respect creeps in.
I personally love hussar though, speed speed speed speed. Even if I have to hit most things twice to kill them.