Personally, I think "evil" and "good" are determined by one's morals, and that a mixture of both is in nature as a whole, not just restricted to human beings - I'm assuming that it's mainly that humans are on a much higher level of intelligence and social understanding than any other organism on the planet (although I can't really back that up, but yeah, two assumtpions in one) that some people think about it that way.
But given the choice on everything about me, I guess I'd rather be more... "biologically animalistic" as opposed to "human", which is why I'm a furry. Part of this is because I'd rather be different in general too, because personally, being the same for so many years makes me think "I'm bored", which is why I'm a fan of transformation. I also believe that subconcious desires eventually release themselves and "expose" your true personality, which leads to some of the things I do that seem more like an animal's behaviour, to not only me but everyone.