Crowds will be lighter in October. Weather probably better in October too, it will definitely be cooler! Although you might stand a chance of a hurricane but I wouldn't let that stop me (and haven't. Rode out one hurricane at Disney and have no qualms about doing it again).
October is the Food and Wine Festival at Epcot. Lots of treats to try even if you don't try the wine or beer. We have been both months and prefer October mostly for the weather, and the F&W is a bonus (not much of a bonus for a 15 month old, but you're going too!)