I'll admit that I'm a Disney fanatic. But I did give US a try. I only had a 1 night stay, but stayed off property (around 1999) after IOA opened. We went to US instead of IOA since it was our first trip to their property. My wife, who isn't nearly as big of a Disney fan as me, was not impressed by US. She prefers the theming of Disney, the queues and the overall experience. For us, Disney is the way to go. I'd like to try IOA someday, but I can assure you it would be a one day visit surrounded by days at WDW. For those that prefer US/IOA, good for you. That's your preference. Mine is Disney. I can respect your choice. US has some decent rides, but they're just not for me.
In a way, WDW actually made Orlando/Central FL. Look what happened after word got out that Walt was buying the land to develop into the resort. The town/area grew like wildfire. Hotels sprang up and other attractions opened all in hopes of feeding off WDW crowds. For 3 decades, when people said they were going to "Disney" they meant Central FL/Orlando. Many people still say it. Are things changing? Maybe. To me, it just means Disney needs to step up and persuade those people that Orlando means WDW more than anything else. US/IOA has the same opportunity. Heathy competition is a good thing.
But in the end, I'll always be a Disney fan! Give me Pirates and Muppets over Kong and Back to the Future any day!