I prefer Maddy, but I'd probably call her by the whole name of Madelyn. In general I'm not a fan of names that can be shortened to an e-sound ending, or shortened at all actually. After a lifetime of being called Susie, Suzy, suzie, etc., I preferred to name my kids with names that can't easily be shortened.
Yes, that is why I named my baby a short name, I don't like it when people shorten names to a nickname. But I actually voted for Maddie. That just makes the most sense in my mind when I read it.