Does Medicaid or Medicare represent a higher risk to the Federal Government Solvency and Debt going forward? I'm trying to understand not only which program is expected to be larger in terms of costs, but which one has the least capacity to adjust (reduce benefits if revenues for the program fall).
Yes, both presents higher fiscal risks up to the future, as they imply in a higher Federal deficit. The hability to adjust depends, unfortunately, not only on the program itself, but in a political risk as the congress could refuse to reduce the revenue to these programs as this would be not appealing for voters. At least USA does not have something like "free healthcare for everyone" written in it's constituition like countries such as Brazil have.
The broader the extent of the program itself determines it's costs.