From personal experience, I can share a few thoughts. We go early February. First, the weather. It is SO much nicer than the potential stifling heat of the summer. We've gone most years in the past 20, and it is very rare that we don't have several days where it's nice enough to swim. We also have the occasional cold front come through, and we've had days where we bumped up our Disney souvenir collection with hats, gloves, and scarves! But most of the time, the weather is nice during the day (shorts/t-shirt, or perhaps pants/light sweatshirt), and chilly at night (pants/sweatshirt). As for crowds, definitely recommend earlier in the month. Once you get to mid-month, it seems to get busier. You'll have the President's Day holiday weekend, Valentine's Day, some years Mardi Gras is in Feb, the race at Daytona brings in people, and they also have the Princess runs later in the month.
Some down sides to early Feb? They often do more rehab work on resorts and attractions that time of year, so you might miss out on something. The parks might close earlier, too. But with lower crowds (traditionally), we get to see/do everything we want. Good luck with your decision!
