We just got back from Orlando and elected to buy an annual pass (which gave us 15 months) to Universal and only used one day of old ten day passes at Disney. My two younger boys had never been to Universal, but have been to Disney tons of times.
They enjoyed the new things at Universal, but I found the lines and the whole Express Pass business sort of annoying. I'm sure we'll go back a couple of times during the 15 months. The 13yo loves the rides and the 8yo loved the characters, particularly Spider Man.
We went about 7PM the first night to get our passes when we could park free. We rode one ride and looked around a bit. We returned the morning of New Years Eve, but it was pretty crowded, so we didn't stay very late. Went back for two short afternoons because the weather was so cold and hit the park shortly after opening yesterday to hit everything we had missed. I think we saw nearly every show and rode every ride in less than four full days. There were even some repeats of the kids' favorites.
If it were up to me, I'd stick with Disney, but even DH enjoyed the different park for a change.
Sheila