Depends very much on circumstance.
Hussars will be good for 'poking' the enemy, harassing and nibbling away at the sides of a formation until it collapses.
Heavies, however, can take 1-2 shots before going down, and can (given a decent chance) ride down a line of infantry and annihilate it very quickly. It simply comes down to training, practice and experience on the riders and their opponents, no type is 'better' than another.