I like the shorter one but only if you want to stray away from a traditional gown. It is delicate which is nice for petite girls.
To be honest the longer one- with all the stuff going on - on the bottom of the dress might be too busy for someone smaller - bigger things look even bigger on petite women.
I would suggest though just try on lots of different dresses. You don't know for sure if a style looks good on you until you try it. For example, I never thought I would like an off the sholder dress - then I tried it on and that was the one I wanted.