@AlphaWolfKiller1. They go about the same speed most of them. Also you will get a unit that is faster than the other units that are the same as it, Eg: Archer going about the speed of a squire , while another Archer is going about the speed of a Paladin. See? There would be to many glitches.
@dariuska10
Actually its not. However it becomes very hard. If you need experience for 1 certain race go to level 6 and send out little hobbits while you arrow is on auto fire. If you do it right you will be done in 5 minutes with 6000 extra exp. =D