Tough choice. Mechanically, in most prior editions, I'd go aasimar all the way; yet I've never actually played one (outside of CRPGs), and have played a half-orc (albeit not in D&D). In the end I chose aasimar, it's just too hard to pass up that divine goodness. And...well, it actually has a chance, however slim, of beating human. Not that I ever expected anything BUT human to win overall...