Unless there are some Disney rides that are on your list of things you really want to ride or see... I might seriously consider Universal if it is all adults. While every Disney park has something for adults, the overall slant for some parks is aimed more at younger kids. MK is very much targeting kids, and while you have a few rides that are for adults they certainly aren't the majority, you'll have Space Mountain and Tron (most likely), Thunder Mountain and if you want the classics you have Haunted Mansion and Pirates. EPCOT has Soar'n, Guardians of the Galaxy and Test Track.. So 3 rides worth doing and that's about it. Studios will give you 2 Star Wars ride, the Tower of Terror and Aerosmith's roller coaster. Animal Kingdom has 4 rides targeting adults, Avatar, Dinosaurs, Everest and a water ride....
Now I will admit that Disney is better at the theme throughout the parks... but for rides Universal is a better deal. Depending on how long you plan on being there I would at the very least do 1 day at Universal. Otherwise you really have to decide what you want from Disney. Are you looking for thrill rides or something else.