I vote after. We've done it both ways. I have two reasons.
First, I hate flying back on disembarkation day--we either have an early flight that we are rushing to meet, or a later flight and are stuck at MCO all day (I know some people do rental cars and drive to disney springs, but I hate renting cars too--too many shuttles to/from the rental place with kids and luggage to wrangle, and I'm tired after disembarkation and don't want to do all that driving). Plus the whole time I am feeling sad because the vacation is over. Going from a resort to the airport is so much less stressful--I can book a character breakfast, take a dip in the resort pool, rely on disney resort bag check in (available at resorts for Southwest, not available for Southwest from cruise), and visit Disney Springs with bus transportation before heading to the airport for an evening flight home.
Second, after my DH got quarantined on our first cruise after the parks, going to the parks before the cruise is one big stress-inducing germ-avoidance exercise for me. I have noticed that we always seem to get sick shortly after the parks, especially in cold and flu season--there are just too many people all in one place, and I'd rather be sick at home than on the cruise where it gets you locked down or worse, denied boarding if you get sick before the cruise starts.