I love both parks equally. I am neither a thrill seeker (luckily some might say given my choice of partner
) or a coaster lover, but I think IoA is great. Spiderman is still one of the best rides at any park, IMHO. I love the theming there, too, especially Port of Entry, The Lost Continent and Seuss Landing. I can't wait to try out the new High in the Sky Trolley Train Ride!
Popeye and Bluto's Bilge Rat Barges are really good fun as long as you don't mind getting (very) wet. The Eighth Voyage of Sindbad and Poseidon's Fury are both well worth seeing.
There are probably more rides I enjoy at the Studios - The Mummy, Shrek 4-D, Terminator 2 3-D, and Men In Black normally feature in each visit. E-T and Back to the Future (which is about to close, if it hasn't already) are both getting a bit jaded, but still worth doing. I've never been a huge fan of Jaws, but it would be churlish not to do it once. Ditto Earthquake. I liked the Jimmy Neutron ride when it was Yogi and ****oo, The Flintstones, The Jetsons and Dastardly and Muttley. I don't know any of the new-fangled cartoon characters!
I've always enjoyed Universal, but I like it even more now that it's a whole destination. CityWalk has some great shops and restaurants and, if you can find time, it's also worth taking a water-taxi to one or more of the resort hotels.