Add that to USF, IOA, Sea World, Discovery Cove, Aquatica (opens in 08), Busch Gardens, and all the other little diversions of Orlando, there is no wonder why millions flock here each year!
As a local, I would like to see a true Giga-Coaster park built here. Something just for thrill junkies. That would seal the deal hands down!
Florida: 4 Disney Parks, 2 Universal Parks, 2 Busch Parks (One isn't exactly central Florida, though...
SoCal: 1 Six Flags Park, 1 Cedar Fair Park, 2 Disney Parks, 1 Universal Park...
It really comes down to your person preference of parks.
SoCal's biggest weaknesses are the parks being much farther apart than in Orlando, as well as increased expense (not for tickets, but for hotels, travel and meals.)
So... in my book, Orlando offers more convenience, and better top-to-bottom consistency. But if you want the very best of the best available between the two areas, I think those options are in SoCal, even though SoCal's got some weaknesses that balance them.
Of course, when Harry Potter opens, then this becomes a blow-out in Orlando's direction.
It doesn't help that our roller coaster park (Magic Mountain) is literally falling apart from lack of even the most basic maintenance. I never liked Knotts either as a kid or as an adult. Their roller coasters were always ridiculously short and most of the rest of their rides were county fair quality. It would be somewhat closer if I could add the San Diego Zoo to the SoCal tally but that isn't a theme park.