It's really a question of money and lazyness. One option is to get a cab or limo from the airport, live on-site (and don't plan to leave the site for anything) and spring for the higher priced options such as Swan or Dolphin. Many who've stayed there say it is great to be able to hop into your room for a quick break.
The other option which I have always used is to get a rental car for the week and stay off-site in a cheaper hotel in Kissimmee. There is a parking lot with shuttle bus service to the conference.
Basically, if the company is picking up the tab and/or you don't want to do much beside the Disney lifestyle, go for the Swan or Dolphin.
If you're paying yourself, or want to do stuff in the evenings and on days before or after the Sphere, consider the rental car/cheaper hotel option.