I haven't gone in May, so I'm not sure exactly what comparison you're making, OP. I can say our fall breaks have shifted from late Sept, early Oct to now land over Columbus Day. Between the change of weeks, the general increase in WDW crowds, Columbus Day week was NOTICEABLY more crowded on my 2014 trip. Columbus Day itself was very crowded and I highly recommend using crowd calendars to pick the right park on that day especially. Been a long time since I traveled in Summer, so I can't compare to those crowds, but Columbus Day easily was as crowded or more than prior spring break trips I've done when my break wasn't also Easter Week.
With a good idea how you'll attack the parks, it's still manageable and fun, but definitely crowded walkways, long lines at certain times, but the weather is great! I'd look at whether food&wine is going on during both options and make my decision based mostly on that and on November weather, which would be preferable to me.