If you are turning 65 or reviewing your coverage right now, you have probably stared at two very different pitches.
One promises low or $0 monthly premiums with extras like dental and groceries.
The other costs more every month but quietly covers almost everything.
Medicare Advantage, also called Part C, is run by private insurers that get paid by the government to manage your care.
Original Medicare plus a Medigap supplement keeps the government paying first, with a private policy picking up most of what is left.
The monthly math is where people get fooled.
A supplement can run $100 to $250 per month depending on your age, gender, and state, on top of the standard Part B premium of $185 in 2025.
Advantage plans often advertise $0 premiums, which sounds like an easy win for a fixed income.
Advantage plans work like an HMO or PPO, with networks, prior authorizations, and copays for each service.
In 2025, the maximum out-of-pocket limit for in-network care is $9,350, and some plans charge more for out-of-network care.
A rough year with a hospital stay and specialists can wipe out a year of premium savings fast.
You pay more monthly, but once you cover the Part B deductible (about $257 in 2025), most plans cover the rest of Medicare-approved costs.
You see any doctor in the country who takes Medicare, which matters if you snowbird or travel.
You get a six-month Medigap open enrollment window that starts when you are 65 and enrolled in Part B.
During that window, insurers cannot turn you down or charge you more for health problems.
That is why the common advice is to start with a supplement if you can afford it, then switch to Advantage later if money gets tight.
The reverse move is where people get stuck.
Once you have health issues, going back to a supplement often means a denial or a sky-high rate.
Add up the worst-case year: monthly premiums, deductibles, copays, and the out-of-pocket maximum.
Ask whether your doctors are in the network, whether you need referrals, and how the plan handles expensive drugs.
Call your hospital and oncologist's office and ask which plans they actually accept.
A handful of states, including New York and Connecticut, give you more flexibility to switch later.
Also confirm whether your employer or union offers retiree coverage, since that changes the math entirely.
The decision is not really about which plan is better.
It is about which risk you can live with: higher fixed costs or higher surprise costs.
Run the numbers for a bad year, not a good one, and pick the one you can survive.
Our take: if you have savings and see doctors regularly, a supplement is usually the safer long-term bet.
If cash flow is tight and you are healthy, Advantage can work, but go in knowing the caps and the network rules.
Final Thoughts
Either way, decide before your window closes, because the deadline is the one part of this choice you cannot renegotiate later.