I Love IOA it has a great coaster in HULK, and a great 4-d ride in Spiderman...the rest is just a SO-SO park...Jurrasic Park is good as is Dueling Dragons...Ripsaw and Bluto are great if you wanna get wet...
If it were me and I only had 1 day I would got the Universal Studios...it has the classic ride that I think makes Universal what it was built to be....Jaws, Shrek, Terminator, ET, MIB, THE mummy, Twister, Disaster, Simpsons....to me from top to bottom its the better of the 2 parks...IOA has a few great rides...Universal has more great rides....ET and THe Mummy are 2 of my favorites anywhere...JMHO