Christmas can be super busy, one of the busiest (yet most magical) times of the year, particularly between Christmas and New years. It's also the Most expensive as your paying holiday season rates and Disney bumps up food and beverage prices as well.
June can be hot but not too bad, you can catch the Star Wars Weekends at DHS the first two weeks in June but unfortunately they moved the flower and garden festival to earlier in the year this year. You will also be in the regular season-summer season range which is less expensive than the holiday rates you will be paying around Christmas. The parks will be less slightly crowded as well.