Our last two trips were May 2004 and Feb. 2005. We are from the Midwest, so it was nice to have heat in May. We liked the hotter weather and spent early afternoons each day at the pool or a water park. The crowd was very bearable. As someone else noted, the flower show was nice at Epcot. There were also concerts going on during the evenings at Epcot, which we enjoyed.
When we were there this past Feb., I did not like the cold nights, which required longer pants and definitely coats. We were there the week before Pres. Day, leaving on the Friday before. The crowd levels were very acceptable (lower) and I think they were better than the prior May. I would imagine the longest wait we had for anything was 20 minutes. We did not plan for a water park, because of the unpredictable weather, and I missed not being able to add this in to the trip. We spent one of the warmest days of our trip at the hotel pool and rented water mice on the lake at our resort, which was great.
I thought both times were pretty comparable trips, with the major difference being the hotter weather in May. If I was you, I would plan it based on resort costs, savings, etc. and take the better bargain. Also, just think how much the next Feb. is to the next May. You would already have a 3-month jump on it if you elected Feb.!!!
Have fun!