When we were deciding, Advantage plans were more like typical employer plans, and you “pay as you go” with deductibles, copays, co-insurance, and caps. Traditional plus Supplement was pricier upfront, but once you reach your deductible, the rest is fully covered (as long as it is a Medicare covered service).
In my state, you cannot change between Traditional plans during open enrollment. You are only are accepted without underwriting for a limited time after age 65. Once on Traditional + Supplement, they can never deny you, or charge you more than someone else of the same age. But, you also cannot change to another Traditional provider without underwriting. If healthy, it usually is no problem. If seriously sick, a new insurance provider does not have to accept you, or can charge more than others. You can supposedly always change to and between Advantage plans, but once in an Advantage plan, cannot return to Traditional after one year.
DH was a resident of another state, so enrolled there. He could switch back and forth between Advantage and Traditional. His premiums, however were much higher than mine, because they average the cost over all subscribers (a 65 year old pays the same as a 95 year old). In my state, rates start low, but rise with age. Cross-over was around age 87 at the time I enrolled.
No question Traditional was more expensive for us, since we’ve been fortunate to have few complications or chronic conditions. We chose Traditional + Supplement to guarantee we can choose ANY MD (as long as they take Medicare), and ANY location (since we split our time between two very different states).
There are more nuances. A GREAT book we found to walk through pros, cons, & options was “Medicare for Dummies” – at least it was when we started looking. Make sure you get the most recent edition, as policies change.