…what would you be, and why?
Dragonborn. Hands down, no question, no hesitation, no apology.
"Always be yourself. Unless you can be a dragon. Then always be a dragon."
Edit: Okay, to actually explain that more than just "omg
I get to be a dragon person and dragons are goddamn cool," dragonborn are both one of the races surprisingly similar to humans in behavior (they don't have the negative associations of many "savage" races, but they also don't have the high-and-mighty implications of many of the graceful/magical races), and yet perhaps the one
most distinct from humans simply because of being covered in scales and such.
They live about as long as humans, but have better healing (at least in 4e), so I'd be more likely to live a decent life but not a "watch all my friends die" life. I don't want to live forever, just a reasonable amount of time, so I can go to meet my Maker in due course. Their proportions are generally similar to tall, muscular humans, other than their feet and hands. Canonically, they don't have tails, so I wouldn't need fancy tailored clothes just to avoid being naked (though, again, shoes would be a potential concern...depends on how durable dragonborn scales are, I suppose.)
More or less, whether this was a sudden spontaneous change of the world, or a "what if you could just have been an X all along and that's just the way the world always had been," dragonborn are distinct enough to feel like a real difference, similar enough to actually get along in human society, and
cool as hell because DRAGONS.