Medicare Primer: Advantage or Medigap?

"Essentially every 65-year-old American enrolls in Medicare, and many get additional coverage. One form of additional coverage is through supplements to traditional Medicare, which include a Part D prescription drug plan and/or a Medigap private insurance plan to cover some or all of Medicare’s co-payments, deductibles, and other out-of-pocket costs. The other is through Medicare Advantage, a managed care option that typically provides prescription drug coverage and other services not included in the basic Medicare program."
So which to choose?
The Squared Away blog offers assistance at: http://squaredawayblog.bc.edu/squared-away/medicare-primer-advantage-or-medigap/