I compared them in the quarterly report thread. Q4 has been the worst performing quarter, in terms of growth over the last 4 years , and now profit is the lowest where it used to be around what they got in the Oct-Dec quarter.
https://forums.wdwmagic.com/threads/disney’s-q4-fy18-earnings-results-webcast.951363/
The results include DL which would skew summer. Anaheim is a lot nicer in the summer than Orlando, and local kids out of school could improve the summer there.
Summer has the least 'extras' and the worst weather. One month of F&W and MNSSHP. Want to wear your costume on a 100degree heat index day? I'd guess they do something for Epcot in the summer, or have a FL resident 3/4 day summer ticket promotion. As a long-time Floridian, I'm planning on going a couple times in summer 2019.