I wouldn't mind if two characters had similar powers, though I would like it if there was a little difference about how your powers worked. 

For example, if two people wanted to be shapeshifters, they could be, as long as they could shift into different things. Like one could only shift into different people (e.g. Mystique) and the other could only shift into animals (e.g. Beastboy). Or the two of them could both shift into animals, but different types of animals. That sort of thing.