I have quite a bit of experience going both weeks. There's no such thing as an ideal week, only pros and cons and your priorities.
My top priorities: prices, weather, convenient (for us), crowds, ride closures.
Choosing between your two weeks is easy. Pick the one that costs LESS!
Crowds are never my top concern, because we can always navigate around them. Higher crowds generally = longer park hours. Longer park hours = more flexibility. As long as your family can use the peripheral park hours, crowds are no big deal. To me, short park hours are no fun. The parks are best after dark.
When MK closes at 7pm, we don't feel like we've gotten our $'s worth. Afternoon breaks are really out, and just ugh! Closed parks = boring nights.
Weather wise, Jan and Feb are similar, but February tends to be a bit colder. ALSO- very important- blizzards are common in both months, especially February. If you are flying to FL, cancelled/delayed flights are common if a big storm is sweeping the USA. those storms never hit Orlando, but they = cancelled Florida flights- because planes can't get TO Florida anytime a storm hits one of the big US cities. Either week, you'll have to pack extra layers.
If you go to Florida in winter, budget for the possibility that you might be stranded there an extra day. It has happened to us a number of times in both January and February. While it sounds fun, in reality, you spend half the day on the phone on hold trying to rebook your flight/car/hotel. None of them are eager to offer discounts, either.
Crowd-wise, your two picks are similar. Pres week is a little busier- because folks stay all week. MLK Jr week crowds peek over the weekend, then drop. When choosing either, your best bet - if possible - is to slightly straddle your visit and go a day early or stay a day late. Missing one day of school pay big dividends when it comes to prices and crowds.
Make your low crowd days commando MK days (do as many e-rides as possible, use all the park hours). On high crowd days, avoid MK and/or spend more time doing low-crowd rides and shows, do your 3 FP, maybe do non-theme park activities, etc.
I won't swim when I see steam coming off the pool or frost. If swimming is a priority- I suggest taking advantage of the warm days you get. Or just skip swimming and water rides. It is no big deal to have Kali River Rapids closed when it is 50 degrees outside. Expect the wet rides to be closed. Plan to see them on another trip. some trips, our first day is warm and that's it. Forecasts don't pan out.
Last, it is worth mentioning a few other items. In addition to those already mentioned: January= football playoffs. Feb can = overlap with the Daytona 500. (an hour form Orlando and = some folks go to both)
