I agree with the others, Islands of Adventure is the way to go. We were down there last week, my kids are only 5 and 7 so we spent most of our time at Disney Parks but did spend a day at Universal. We got a $85 unlimited pass at AAA for unlimited in both parks for 7 days. We only spent one day, but did hit both parks, the coasters and other rides looked awesome at Islands of Adventure. The Spiderman ride was pretty cool, kind of like a simulator with 3-D thrown in, my 7 year old was a little freaked out when Spidey landed on our car and pulled off his 3-D glasses. I wanted to do the Hulk Coaster real bad, but never got the chance, we spent our time at Suess Landing.
At Disney, each park may have a couple of rides for the older crowd, but not much more. For example, Animal Kingdom has expedition Everest which is really cool, but not a whole lot more as far as rides go.
Universal was much less crowded as well, there was a little kiddie coaster in the regular Universal that my kids liked, so we road it about 6 times in a row with no wait at all. Most of the waits at Islands of Adventure for the bigger attractions were around 20-30 mins. That was on a Friday, weekends may be more crowded. If you get there right when it opens, you can get a lot of rides done in the morning.