Several days ago, Matthew Yglesias dug deeply into the Medicare weeds, arguing in Slate that Obama and Ryan basically agree on what needs to be done to Medicare costs. “They have essentially the same plan to control Medicare spending. And it’s a pretty good one,” Yglesias told his readers. Hmmm.

I don’t agree with Yglesias, or at least with the implications of the headline Slate stuck on his piece: “Obama and Romney Agree on Medicare; if you ignore the fiery campaign rhetoric, you’ll see an astonishing level of consensus.”Just because Ryan and Obama agree on the same spending targets does not mean their approaches are anywhere near equivalent. Medicare now is social insurance that guarantees a set of benefits to everyone 65 and older, and to disabled people. Americans have an obligation to pay into the system when they are working and have a guaranteed right to receive benefits when they are eligible. The GOP approach would convert Medicare to a private insurance scheme. The government would give people a voucher with which to buy insurance from commercial carriers. That’s a huge difference. Under a voucher plan, insurance companies may or may not have to provide a minimum set of benefits, and people would essentially get what they are able to pay for.

But Yglesias does raise an important issue about not only controlling the cost of Medicare, but controlling medical costs period, the elephant in the healthcare room.

He described current Medicare spending this way: “It’s almost as if the government had a program that just gave senior citizens free shoes in unlimited quantities,” adding that the program offers an open-ended commitment, which expands as new healthcare technologies are invented and existing services get more expensive. He’s right; it is open ended, and has been since the program began. And while we’re talking history, it’s worth noting that healthcare providers have pushed back, often successfully, whenever Medicare tried to control its costs.

What to do about this now? Yglesias reports that both camps agree that spending must be trimmed, and both believe Medicare should grow at a fixed rate—one half of one percentage point higher than GDP growth. They just disagree on how to implement the cuts.

Yglesias notes that in the GOP plan, the growth target would limit the size of the voucher. If it’s not enough for seniors to buy what they consider a decent policy, they’d have to pay the rest of the premium out-of pocket. And the CBO, in scoring Ryan’s first version of a voucher plan, found that the plan would cost seniors several thousand dollars more than Medicare. (The CBO has not scored his second version).

As for Obama, Yglesias reports, the president’s reform would instead “hit the growth target the way foreign single-payer systems limit their costs, with more aggressive bureaucratic management of what Medicare is willing to pay for and how much it’s willing to pay.” That is how most national health insurance systems, whether single payer or multi-payer, spend a lower proportion of GDP on medical care (while, by the way, often achieving better patient outcomes).

Who would bear the burden of Medicare cuts under each approach? Yglesias doesn’t explicitly say, but the point is a critical one. Although neither party would agree to this somewhat reductive language, in short, Ryan wants to reduce the government’s check to Medicare beneficiaries. Obama, meanwhile, wants to reduce government checks to doctors, hospitals, and others who provide the care.

Under Obama’s vision for Medicare, presumably, the program’s fee schedule would still exist, although provider fees would grow at a lower rate. In the absence of any plan details from Ryan, or an actual bill, we are left to wonder what the cost control mechanism for Medicare providers will be in the GOP’s vision. Under a voucher plan, there may be no control or oversight on what doctors can charge seniors. Will their fees reflect what the market will bear?

Trudy Lieberman is a fellow at the Center for Advancing Health and a longtime contributing editor to the Columbia Journalism Review. She is the lead writer for The Second Opinion, CJR’s healthcare desk, which is part of our United States Project on the coverage of politics and policy. Follow her on Twitter @Trudy_Lieberman.