My instinctive answer is that both/either week should be fine. I haven't heard of any major events during those weeks that are likely to result in huge crowds in the parks.
April 30 - May 2: This should be after Spring Break, but before summer starts. I would expect medium length operating hours, with nighttime entertainment occurring only on weekends. The "Frozen Fun" event should still be going on in DCA. There may be some last minute refurbishments occurring in advance of the 60th anniversary. No major holidays come to mind during this period that would result in high(ish) crowds.
Nov 30 - Dec 4: The Holiday season should be in full swing, with fireworks and WoC occurring nightly. Fantasmic and Mad T Party (or whatever they add in it's place if it doesn't resume after Frozen Fun ends) may still only be occurring on weekends. The parks should be operating with medium-long hours. If 2015 is anything like 2014, there might be a few events in the latter half of the week or starting the next week that might result in slightly higher crowds. The biggest event is Candlelight Processional, which typically occurs the first weekend in December. That impacts some DL attractions and results in high crowds on MS. Weather is more likely to be cold(ish) and there is a chance of rain in late Nov/early Dec.
Personally, if I had to pick one, I would probably opt for the Nov/Dec dates because it's during the Holiday season at DLR. Apr/May is fun (DLR is always fun), but it's less likely that anything "seasonal" will be occurring (Easter/Spring will probably be over and it's not clear when 60th anniversary events are starting).