LF - I would opt for the space center. Transit time from port to Epcot would probably be around 75 minutes each way with little traffic. Add time to enter and exit the park and the fact that you never really get the full advertised port time by the time the ship clears customs, etc. You really wouldn't get too much time in the park. There is so much to see I can't imagine teasing myself for 4 or 5 hours.
All I ask is a tall ship and a star to steer her by; John Masefield
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014, Regal 2014, 2016
Star Clippers: Royal Clipper 2015