My personal preference is WDW first for 5-7 days, then a 7-day cruise just because, as others have said, it's nice and relaxing afterwards. But we've done cruise first/WDW last, WDW first/cruise last and WDW/cruise/WDW. We've done 3-day, 4-day and 7-day cruises combined with WDW for as few as 2 days and as long as 8 days. For us, it largely depends on schedules - when I can take my vacation (time of year, day of week), flight schedules and costs, cruise schedule, resort availability, stateroom availability and costs, etc. We always come in at least a day before the cruise. If it's a cruise first, then we stay at MCO Hyatt. If it's cruise last, we stay at WDW.
We have friends who live near WDW, and we like to see them when we go to Florida, but they can usually only see us on the weekends. On our upcoming vacation, our plan was to do WDW for 6 days ending with the weekend, then a cruise for 4 days. The flights leaving MCO on disembarkation day were either 11 am (too early) or 7 pm (way too late). I'd been trying to figure out if we should stay at MCO Hyatt after leaving the ship, but we'd get to the hotel way too early to check in, so we would have to sit for a few hours waiting for a room to be ready with nothing really to do. If we went to WDW for that night, we'd have barely one day in the parks and I couldn't stay longer due to work schedules. But our friends said they'd cruise with us if we did it on the weekend, so now it's 3 days at WDW, 3 day cruise, 4 days at WDW which actually works out better for us.
We once had a credit card benefit that would cover up to $250 at a hotel, and we'd lose that benefit if we didn't use it by a certain date. we tried to figure out where we would go to use it before expiry and came to the conclusion that the MCO Hyatt would work. That obviously meant we had to take a cruise followed by a few days at WDW (my story, sticking to it), so that's how that planning came about.
There is no right or wrong way to do it, and regardless of my preferences, logistics usually makes the decision for us.