Basically the two head units are doing the same thing/ job....the first one--basically stocks use the grooves and stuff on the lense to direct light to the right places on the road.
the second one the so called "racing " heads used rear reflectors to direct light to where it's needed on the road.
without either system, the lights would go every which way...up, down , left, right....and you don't want that, you want it focused on the road and not on the eyes of on coming traffic.
people here clear their heaht lights but that's ususally because they are getting HIDs or what not--projecotrs.
it's more on tastes...pick the one you like.