The article does mention doctors in-network: “Each Medicare Advantage plan is different, so you need to compare plans’ co-pays, doctor and hospital networks, and how they cover your drugs”.

Medicare Advantage plans are run by private insurance companies and
can be more costly than using a medigap plan if a person gets sick,
cancer being the most costly illness. Medigap at $136 per month x 12
months = $1,632 per year for a plan F. With a plan F medicare
supplement, a person has no co-pays for medical services covered by
Medicare. Compare that to $5,000 to $6,700 out-of-pocket caps with
Medicare Advantage plans.

The answer to Jonathan’s question about Part D is: Most Medicare
Advantage plans include Part D and they operate in exactly the same way as do stand-alone Part D plans. Both have co-pays for each drug tier and both have the donut hole.

Most Medicare Part C (Medicare Advantage) plans include a Part D plan built in and they do “feature” the same donut hole.

This article is strangely prejudiced against Medicare Part C and in favor of Medigap.  It implies that Medicare Part C is private and Medigap is public when the opposite is true.  

It makes Medicare Part C sound like some odd approach to insurrance.  If you are turning 65 — as the article says at the beginning — you will find Medicare Part C just like insurance you have had all along from an employer with reasonable co-pays and similar rules, the most important of which is an annual out of pocket limit on how much you can spend.  It’s Medicare and Medigap that are different and that do not have OOP or lifetime limits (althought you’d have to be very sick to max out a Medigap policy)

But the article also does not mention the major thing to consider when deciding whether to use the usually less expensive Medicare Part C approach: does your doctor take it?  Most Medicare Part C plans rely on networks of formally or informally tied together doctors and you can’t go outside the network.