I personally feel that DISmounting can be a little, if not a lot faster. The thing which especially doesnt make sense, is the fact you have to stop before dismounting, rather than the ability to jump of at most of the times. Ok would be difficult with full plate, I admit, but if encumberance is added and tweaked against the speed + agility - weight etc. I'm sure it would make more sense for people to be able to jump off their horses a lot faster..