The structural difference in one paragraph
Original Medicare is a federal entitlement — the government pays providers directly per the Medicare fee schedule. Medicare Advantage is a private insurance product that the government pays a per-member-per-month fee to in exchange for the carrier providing all your Medicare benefits. Both deliver Medicare coverage, but the structure changes everything: networks, prior authorization, drug coverage, costs when you actually use care, and what happens when you travel.
Path A — Medicare Advantage (Part C)
One bundled plan. The carrier handles your Part A, Part B, and usually Part D. You pay either $0 or a low monthly premium, plus copays when you use services. There's an annual in-network out-of-pocket maximum (typically $4,000-$8,000 in 2026) that caps your annual exposure for in-network medical services.
What's good about MA:
- Low monthly premium (often $0); drug coverage typically bundled
- Annual in-network out-of-pocket maximum that Original Medicare doesn't have
- Often includes "extras" — dental, vision, hearing, gym memberships, OTC allowances, sometimes meals after hospital discharge
- Single ID card, single insurance company, simpler to navigate
What's not good about MA:
- Network restrictions. HMO plans require you to stay in-network for non-emergency care. Even PPO plans have significantly higher out-of-network costs. If your specialist isn't in-network, you pay full price.
- Prior authorization. Per the 2025 State Medicare Scorecard, the percentage of MA plans requiring prior auth for specialist visits varies from under 10% in South Dakota to over 70% in Washington. Prior auth means your doctor has to file paperwork before the plan will cover the service — sometimes leading to delays or denials.
- Geographic lock-in. MA networks are usually local. Snowbirds and travelers often discover their MA plan doesn't cover a specialist in their winter location, or covers them only at out-of-network rates.
- Plan instability. Networks change yearly. Premiums change yearly. Drug formularies change yearly. Your perfect MA plan in 2024 might not include your hospital in 2027.
- Annual reshopping required. You should re-run the comparison every Open Enrollment to make sure your plan still works for you.
Path B — Original Medicare + Medigap + Part D
"Unbundled" — three separate pieces. Original Medicare covers Part A (hospital) and Part B (outpatient). A Medigap (Medicare Supplement) plan from a private insurer covers most of Original Medicare's gaps — coinsurance, deductibles, hospital days beyond Original's limit. A standalone Part D plan covers prescriptions.
What's good about Path B:
- No networks. You can see any doctor, hospital, or specialist in the U.S. that accepts Medicare — and most do.
- No prior authorization for most services. Original Medicare almost never requires prior auth for covered services.
- Predictable costs. With Plan G, you pay only the Part B annual deductible ($257 in 2026), then your share for almost everything is zero. Plan N adds small office-visit copays but otherwise similar predictability.
- Medigap is portable across the country. If you move, your Medigap plan moves with you with no network change.
- Standardized coverage. Plan G from any carrier covers the same things as Plan G from any other carrier — so you shop on price, not features.
What's not good about Path B:
- Higher monthly premium. Plan G premiums in 2026 run roughly $115-$280/month for a 67-year-old non-smoker depending on state and carrier. Plus the Part D plan ($0-$80/mo). Plus your Part B premium ($202.90 standard) — though that one applies to everyone.
- Three separate billing relationships. One Medicare card, one Medigap card, one Part D card. Three premiums if you're not on auto-pay.
- The Medigap window matters. Outside the one-time 6-month Medigap Open Enrollment, carriers can apply medical underwriting in most states.
- No "extras" by default. Dental, vision, hearing not included — buy those separately or pay out of pocket.
The actual annual cost comparison
The marketing pitch makes MA look like a no-brainer: "$0/month vs $135/month for Plan G." But the comparison only matters in total annual cost including what you actually use.
For a healthy 67-year-old with no chronic conditions:
- MA-PD (typical): $0 premium × 12 = $0 + ~$300 drug copays + maybe $1,200 in typical medical OOP = ~$1,500/year
- Original + cheapest Plan G + cheap Part D: $135 × 12 + $0 Part D premium + ~$500 drug copays + $257 Part B deductible = ~$2,377/year
Path B is ~$877 more per year for someone with no health issues. But for someone with a chronic condition who actually uses specialty care:
- MA-PD with multiple specialists: $0 premium + $1,800 drug copays + $4,000 OOP max hit = ~$5,800/year
- Original + Plan G + Part D, same specialists: $1,620 Plan G + $0-300 drug copays + $257 Part B deductible = ~$1,900-$2,200/year
Path B is now $3,000+ cheaper for the high-utilization year. Plus no network restrictions, no prior authorization for most services, and full predictability.
The framework most agents won't articulate
Choose Medicare Advantage if:
- You're healthy and expect low utilization
- Your doctors and hospitals are in-network for an MA plan you've vetted
- You want the bundled extras (dental, vision, hearing)
- You prefer one ID card, one premium, one insurer
- You don't mind re-shopping every Open Enrollment
Choose Original + Medigap + Part D if:
- You expect higher healthcare utilization (chronic conditions, frequent specialists)
- You want freedom to see any provider that accepts Medicare
- You travel or split time between states
- You want predictable annual costs without surprise prior-auth denials
- You'd rather pay a higher premium than fight with insurance over coverage
The cost of getting it wrong
The expensive way to get this decision wrong: pick MA at 65 because the premium is $0, develop a chronic condition five years later, try to switch to Original + Medigap, and discover you can't get Medigap without medical underwriting in most states. Now you're stuck on MA, paying maximums every year, with whatever network restrictions your plan applies.
Outside Connecticut, Massachusetts, Maine, and New York — where Medigap is guaranteed-issue year-round — switching from MA to Medigap after the one-time Medigap Open Enrollment closes is often blocked by underwriting if you've developed any health conditions.
What to do
Run the comparison for your specific situation. Our tool shows both paths side-by-side with the math, against your actual zip code, your actual medications, and your actual income (for IRMAA). The difference between paths is rarely small. The difference within a path — picking the right Medigap carrier or the right Part D plan — is also rarely small.