Hi Michelle! I don't think you can go wrong with either of those choices, honestly!
We actually love to cruise in the winter (November through February), as the temperatures in the Bahamas and Caribbean are still wonderful (mid 70's to 80's), and we tend to get better prices when we cruise then. If you're dates are flexible, play around with the different
cruise itineraries for those times on Disney Cruise Line's website and see when you can find the best price.
Though some at-sea days tend to be cooler, once you're actually in the Bahamas and Caribbean and at the ports, I'm sure you'll find the weather to be wonderful! We always have! That being said, I'm certainly no meteorologist, so there could always be a cold spell, but for the most part, it's warm and sunny in those ports year round! I do always bring a light jacket or sweater for chilly or windy sea days, but I'd recommend that in the summer as well.
Have fun planning, and once you book your cruise, please let me know if you have any other questions!
I'd love to help!