The shorter the puffer the more sporty it looks, and the longer, the more ladylike imo. Longer puffers are more versatile as you can wear them with tunics and shirt dresses (as a fellow mom, I know you must have a few of these).
I try to avoid horizontal quilting to avoid the Michelin man feeling. I think an angled chevron quilting can be very flattering, or others that feature some kind of contouring. Also look for some elastic on the back to provide shaping.
Here is an example below from Laundry by Design. I have two Laundry coats and like them very much. They also have puffers made with, Thermatec, a down-alternative option that I've found to be very warm:
http://shop.nordstrom.com/s/la.....color=BONE