Speaking as a reader -- size, as they claim, doesn't matter. What matters is quality; that is, are you just listing traits like "She was a dark-haired woman with high cheekbones, and she loved to kick puppies every chance she got," or are you actually showing her kicking puppies as her ebony locks sway with her every movement and the corners of her mouth turn up in a satisfied smile? Also, if that's the protagonist, I can't wait to see the antagonist.

Speaking as a writer -- if you're just doing it for yourself, keep it short and easy to reference later.

Speaking as an occasional Contest Round judge -- if you're going to write a 5000 word intro story and you wouldn't mind winning the contest, it had better be damn intriguing or the judge will just move on to the next one.