Most of my characters are magic or tech. A close second is mutant, followed by natural, with science being a distant 5th. I find tech or magic far easier to explain away. To me, "mutant" means you always had that ability/potential, whereas science is some process/accidental exposure that causes the powers. "Natural" is the toughest, because it already stretches credulity to believe any CoH character could *not* rely on magic, tech, or some other form of enhancement to survive. The only exception would be that I consider "Natural" to encompass any traits that a character would have due to their species. So for instance, an alien that can project energy because of their innate characteristics would be natural, and even something like a demon whose abilities are due to their demonic nature, (and not explicitly learned magic/alchemy), would also be natural...