We have United Health Care (AARP-affiliated) since it was a good price for a supplement with the discounts they offer for the first 5 years, and they offered a *wide* range of individual plans (currently Plans A through N**) to choose from.
We did not want Medicare "Advantage" because there are significant disadvantages (which they won't tell you about) including if wanting to go back to a supplement it can be done only once a year and even then in most states you'd usually have to may be subject to additional “underwriting” (which is evaluating your previous health, etc, and you may "pass" or not, or have higher rates).
And we did not want an HMO because the doc's and hospitals you can go to are limited to that particular HMO's docs/hospitals/locations, a "referral" is needed from your primary care doctor before you'd be "allowed" to go to a specialist (and they may not give it), etc. At least in this area, the main HMO is the best in the country...but elsewhere they vary a lot in quality.
Having a supplement (Medigap) is the only way to go in my opinion if you want the widest choice of doctors and hospitals, better coverage for all kinds of health issues, less having the company not cover this or that or hassling you about covering it, etc, etc.
Medicare Advantage and HMO's are both private so their intention is to spend the least money they can to increase their own profits.
** http://www.medicaresupplementalinsurance.com/medigap-plans-a-through-n.html
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