Hello bayarea58,
You are right about needing to know the underwriting policy.
At approaching 65 there is much research and a lot to understand.
The Supplement Plans, A - G , are easy to comprehend, grasp and understand.
The Advantage Plans can be as different as night and day from one insurance carrier to another, as different as the Insurance Carrier itself.
If you choose Original Medicare with a Supplement Plan and Plan D, drug plan, they all work together.
If you choose an Advantage Plan you know longer have Original Medicare you have a typical insurance carrier plan and the insurance carrier more or less calls the shots and there are big differences, usually in how much they pay for certain medical needs compared to the Original Medicare with a Supplement and D Plan and as well another difference is where you can go for medical care etc. especially how it works if traveling in the US or overseas.
Once you choose a Supplement Plan to go with Original Medicare and you want to change to another carrier's Supplemental Plan down the line you must go through underwriting which you do not have to do at age 65, all pre-existing health problems are covered if you sign up for either , the Supplement or the Advantage, at age 65. However if after you have a Supplemental Plan and you want to change and have developed a medical problem, after having signed up at age 65, that they consider 'a risk', they have the right to turn you down, meaning the insurance company you were trying to change to.
With the Advantage Plan it is all inclusive, medical and drugs. You can switch once a year during open enrollment to another Advantage Plan, another insurance carrier. No underwriting from what I understand.
With the Supplement Plan you can choose , once a year, another Plan D, the drug plan, if you want and need to. Again, with the Supplement Plan, the medical part, and wanting to change carriers, it will have to go through underwriting and you can be turned down.
With the Supplement Plan it is typically, a larger amount for the monthly premium vs the Advantage Plan monthly amount, the premium. However with the Supplement Plan it is a very small deductible annually, the Original Medicare Deductible amount. The Advantage Plan is usually a large annual deductible with co-pays etc. They tout bells and whistles, but one must truly understand all.
So if you eventually become one who has to go to the hospital due to ones health or an unexpected injury, you pay the 'large' deductible yourself every year with the Advantage Plan vs. a small deductible with the Supplement Plan. There are other differences also, especially if you need more than 20 day in a rehab facility. Supplement Plans give you many more days and most people need more than 20 days to get it right and complete.
I hope that this somewhat answers what you were wondering about and hope I explained it where it makes sense. By the time you sign up it could have all changed...or it just might change this year ( I doubt that, however) with all the changes being talked about politically.
Barbara