In 2012 I went in May for the first week of Star Wars weekends, and in September (20-23, if I remember correctly?)
I much preferred May.
Weather was MUCH better. Crowds seemed about the same to me, except in HS around the Star Wars stuff.
I also enjoyed going to the Flower and Garden festival, which had it's last weekend while I was there.
We did the Mnnshp in September, but it POURED rain, and they had to delay the parade and fireworks, cancel some of the smaller shows, and didn't even do the headless horseman for the parade. It was disappointing.