Every time of year has pros and cons. The seasons that are designated as 'value season' by Disney are that way for a reason.
September's one example. It's hot, it's hurricane season, and most folks don't want to pull their kids out of school during the very start of the school year. Plus, even if there's no hurricane, there is almost certainly going to be rain and thunderstorms.
Christmas is the highest of high seasons. I suppose some would say it's a magical way to spend the holiday - but the prices are crazy high, the crowds are crazy high, and the weather can be rather cold. You're also mixing a traditionally uber-religious holiday with uber-commercialization. Outdoors in the cold all day is not my ideal time to go. Cold temps continue in January - along with lots of ride rehabs. But you'll get low prices and low crowds.
Spring brings mostly high crowds, and fairly high prices, but the parks inthe spring are just lovely. Being nice and warm after acold winter feels great. then you come home to spring- longer days and warmer weather...It's a good way to minimize the post-Disney blues.
October is also pretty nice- moderate prices, reduced hours , F& Wine Festival (depending on how you feel about intoxicated guests all over Epcot), but also reduced park hours and LOTS of Halloween parties (They require paid admission, which adds up, otherwise you're shut out of MK most nights.) You come home to late fall/winter.
Generally school vacations are going to be more crowded and more expensive: any holiday and summer. You've also got to look at average weather for each month. Disney special events: races, festivals, etc.
I've been in most of the months of the year: Feb, Mar, April, May, July, Aug, Spet, early Oct, November, early Dec. January and June hold no appeal for me. Again I say, every time of year has pros and cons. There's a price for lower crowds, and that price can be steep.
