From my understanding, which is mainly just the differences between them is that U. Amph gets bigger but is less aggressive. It will accept a much wider range of conidtions and spawn without too much fuss in home aquaria. As opposed to U. Fernandez which will stay ~4in smaller and fight back anyone who bothers it, requires a low ph and requires specific conditions to produce viable fry. Both a relatively peaceful in the cichlid department being comparable to severums, with probably less conspecific aggression.