My preference is Fall.
But only if you're ok with being away from your family for Halloween, Thanksgiving, and Christmas.
But other than that, it is an amazing experience.
You get the Mickey's Not So Scary Halloween Parties at MK... and everything else fun that goes along with that festive time of year. Orlando offers fun stuff too, like Universal's Halloween Horror Nights you can do on a night off.
Food and Wine Festival, which is obviously amazing - at Epcot. They also have good bands that come and play for that.
Mickey's Very Merry Christmas Parties at MK, Dancing Lights at DHS, Candlelight Processional at Epcot, etc. etc. etc. during the holiday season. And seeing the castle decorated for Christmas is truly magical.
And the weather is still nice. I was laying out at the pool in December.