We went to Disney the first week of March in 2007 and the first week of May in 2008. What a difference, for us at least! In March, we were wearing pants and long sleeve shirts many of the days. Several days started out in the low 60's. It did warm up during the day, but we were pretty shocked at how cold it actually was. In May this year, we approached 90 on most days. I think the crowds were fairly similar both times of year. But in March, we were there before the spring breakers arrived. If I were to choose between these two, I would go in March just because we like touring the parks in cooler weather rather than in the heat and humidity. But we're from Maine, so I am sure that is why!