We just returned from our 1st September trip.
Have done most of the fall, winter and spring months, we all loved September.
for September, weather is great and crowds are low.
I've only been in May once, yet we will be returning this year. I remember May as being warm, and crowds large while we were there. We are returning in May for Star Wars Weekend so I'm expecting crowds.
A few years ago we did October and the weather was also very good while we were there but it was during the F&W Festival and Epcot was very crowded. During our September trip we enjoyed Epcot so much more because the crowds were so low.
I think weigh your options on what your looking for, September is a quiet month and it's also value season with lots of deals on resorts. Weather is on the warm side and humidity can be high at times, yet crowds are low, also MK host
MNSSHP on special nights. We were there for 8 days and only caught 1 late afternoon shower that lasted for a few hours.There is only one negative feature towards the end of the month and that the lovebugs. They are a nuisance.
I expect larger then normal crowds in May this year. Disney has something going on during the middle of the month, not sure but I think it D23 or something like that. Also expect larger then normal crowds towards the end of the month with the opening of the new Star Wars Ride, plus the DHS host Star Wars Weekends towards the end of the month so expect larger then normal crowds on those weekends.