I think you could derive an interesting plot alone from the differences between the classes of magic that have similar resultant effects. In mutation-based roleplays of mine, it was always a large source of interaction when two similar abilities met and even more so when their roleplayers had positive IC interactions instead of conflicts. For instance, I had one character with a large, mutated arm that allowed him to manipulate fire, while another one simply had a type of pyrokinesis. With some close supervision and some world-scale decision making by the GM, this interaction actually opened up and answered a plethora of questions surrounding those abilities and how magic/mutations worked in the world as a whole.