Other than the fact that one is exclusively male, and the other exclusively female, Tauros and Miltank have very little in common physically that would warrant a prevo.
actually they do have a lot in common they are based on the male and female cattle... miltank=cow tauros=bull a calf Pokemon would fit right in
also am I the only person who thinks the new Eevelution is a normal type? (all the moves used appeared to be normal type moves)