The New York Time reports that Congressmen of both parties are skeptical of President Obama's plan for an Independent Payment Advisory Board (IPAB) to determine payment and coverage decisions for Medicare: "Obama Panel to Curb Medicare Finds Foes in Both Parties".
But that's because the Congressmen want to retain that authority for themselves -- not cede it to the executive branch.
There are many problems with an bunch of unelected "independent" bureaucrats making such decisions for all senior citzens, as the Wall Street Journal points out in "The Other Medicare Cutters". The lack of accountability is dangerous and would quickly lead us down the road to explicit rationing.
But the solution is not to have these decisions made by politicians subjected to pressure-group tactics. That will merely lead to a feeding frenzy of lobbyists seeking to have their pet benefits covered by Medicare (and those of their competitors excluded from coverage).
In other words, there is a false alternative in the question, "Which branch of government should decide what health care benefits should be covered and what the payment should be -- the Congress or the executive branch?"
Instead, the answer should be, "Neither!" Government shouldn't be making such decisions at all. Rather doctors, patients, and insurers operating in free market should decide.