Given a choice between the two, I'd pick IOA.
But I had to stop reading the poll thread after the first page. I get very tired of hearing the WDW lovers in the other boards bashing the Uni parks. "No magic", "It's for teens", "nothing there for me", all comments that sicken me, because there is magic at Uni - some people are simply too thick to see it unless it comes packaged with Mickey Mouse on it.
And yes, USF and IOA are both geared toward an older audience, and have less for 4-year olds to do than MK. But then, the same can be said of Epcot, MGM, and AK - and many people with really young kids DO say those things about the other Disney parks - "half-day park", "doesn't really hold my interest", "kids found it boring", "Disney really screwed up with this one." Rubbish!
MK is my least favorite of the WDW parks. I love MK, I just love the other parks more - but what the heck is it about MK that turns people into fanatical, drooling devotees who can't seem to find any joy, any happiness, or any fun in any other park in the world? Why does MK inspire people to cast aspersions on the other parks, particularly the Uni parks, some of which are not only baseless but can be downright nasty?
I guess it must be the childhood thing - MK makes you feel like a kid, which to me is all about uninhibited fun and wonder (which is what Walt always aimed for), but to some people being a kid is all about calling other kids ca-ca-poo-poo-heads.