Atypical, but like just about anyone here. Our habits are almost never going to reflect true trends. Particularly those that have AP's, etc., like I believe you have (that makes a tremendous difference in overall costs).
It would be really great if we could get data on that. From my anecdotal experience being the "point person" in my social/work groups about Disney, people are picking one or the other. I always help them lay out all the choices (at first it stung quite a bit that folks would even consider Orlando without Disney, I'd get this pang of "that's really too bad..." but I've gotten used to it).
But when you do the numbers, it's just so expensive to do both, and Disney's incentives to keep you staying longer (the 5 for 7 deals, or the ticket pricing structure to begin with where there isn't a significant difference once you get to a certain amount of days) and pretty much insistence that you stay on site, that folks feel like they'd essentially be paying for two vacations when an Orlando theme park vacation is so packed and anti-relaxing to begin with. Even when you price out staying at one off-site hotel the whole time, when you then add a rental car, and parking every day, etc. - and the thought of spending the entire trip racing around in a car - it makes the decision for them.
And the thing is, the people who come to me are the "new audience" that is among the new 14ish% of folks being brought into the area. People that have never been, or have been to WDW once ten or eight years ago, and have either never or only once been to the Universal parks. Universal is almost always their #1 interest (the must do) because of Potter, etc.
Again, though, that's my completely anecdotal experience, but when you sit down and look at the numbers, you see why folks would think that way. I really wish we had data on this sort of thing because I believe this is really the story here.