One thing to note is that on item 2 you can see any doctor in the US (that accepts Medicare and for which Medicare covers your condition) without preauthorization and Medicare will pay for it, and your Medicare supplement will pay the remaining amount (depending on if it is a Plan G/F, and N if it is not an excess charge service, and if not then you will have more of a payment to meet a higher deductible with the other Medicare supplement plan types ). Thus you choose who is best for the medical condition you have, and not an insurance company. That is the key advantage of Medicare with a Supplement over a Medicare Advantage plan (I , as other posters, have already mentioned the pros and cons of these two insurance types)
I didn't look back too carefully at this long thread so this is probably covered already but here I go.
Supplements do a very good job of covering the 20% co-insurance, deductables etc and limit the out of pocket risk so it gives a predictble expense for medical.
However they cost a fair bit more than a Med Adv/Part C.
They also don't cover drugs which is mandatory (additional expense $100/mo) or lifetime penaties apply.
Supplements also do not cover dental, vision or hearing meaning an additional policy.
I have chosen a Med Adv plan with 0 premium.
Had all six major joints replaced, glasses every 2 years, hearing aids every 2 years, almost no drug costs.
Never have I come close to the out of pocket maximum. Add to that a couple of ER visits with minimal cost.
I do however conform to their network of providers (out of state urgent or ER is covered) but that is a
very wide set if you use the 2 largest insurers (UHC & Humana).
I also do not need specialist referrals.
Sometimes there is a preauthorization but it is quick and I have never been turned down.
Plus out of network can be covered but at an increased co-pay/co-insuranse.
Each person has to look at whats best for them.