As one example, many opponents of the Ryan "premium support plan" claim that it cuts Medicare benefits, while the Affordable Care Act did not cut benefits. See for instance Eugene Robinson in the WaPo who says this:
"The Affordable Care Act, otherwise known as Obamacare, slows the rate of growth of payments to Medicare service providers by more than $700 billion over a decade. But no impact is felt by seniors themselves, whose benefits and costs remain the same."
Sarah Kliff, in an otherwise very informative post, makes a statement that is very similar:
"It’s worth noting that there’s one area these cuts don’t touch: Medicare benefits. The Affordable Care Act rolls back payment rates for hospitals and insurers. It does not, however, change the basket of benefits that patients have access to."
Now current Medicare does not pay anything directly to beneficiaries; the beneficiaries visit hospitals and doctors, who are paid directly by Medicare. ACA does cut payments to doctors, hospitals, and some private insurers, and Kliff's otherwise fine post details quite well what those cuts are (they are very complex). To say that ACA's cuts to doctors, hospitals, and private insurance companies (who provide supplemental Medicare insurance) are not cuts to benefits is really semantics. Taken to an extreme, ACA could have cut doctors' reimbursement rates to Medicaid rates (extremely low, that is) and the ACA sympathizers would still be saying "but we didn't cut any benefits."
Getting back to the Klein interview of Rep. van Hollen, there is this exchange. I like Klein's question more than van Hollen's answer, which doesn't really address the question (though he does have a valid point on what ACA attempts to do).