text:  Traditional Medicare isn't much use without a supplemental plan. Most often, people choose Medigap, a plan provided by a private insurer that fills the gaps in the coverage. Because most doctors take traditional Medicare, with this combination, you can see anyone. The world's your medical oyster. The other path for seniors is Medicare Advantage. These plans are run by private companies and can offer extra benefits and lower premiums. Why do so many seniors choose Medicare Advantage?