They really do not compete. BGT is officially certified as a zoo with the Government. BGT also gets visitors from the beaches at Clearwater who don't venture to Orlando. Besides, they are in the Orlando Flex ticket together. There is a clearly different market of visitors that hit Universal and Busch Parks. They want 'attractions', good food, shows, etc. Rides and games are the after thought.
Disney caters to the people who want the total resort experience. No car rental, no fuss, nothing. The other parks get the people who are more experienced with Orlando, like myself, who will drive International Drive, beach it at Clearwater or Daytona, and see the other attractions like the Space Center, Gatorland, Silver Springs, and Cypress Gardens that offer a change of venue.