Odds are with you that you can swim with either time frame.
However, weather is a fickle creature and you can never say for certain what will happen. Especially when you start to talk about Fall/Winter or Spring in the South (Summer is the only given, where it's hot)
There are higher odds of a cold snap in November than in October but there are higher odds of a Hurricane in October than in November.
Pools at Disney are heated so even if the air temps are not super warm you can likely get in, just have a cover up for getting out. We were there in early Oct for a week this past year and it was only warm enough to swim at the start of the trip. Last few days it was not.