The legislation created four tiers of insurance — bronze, silver, gold and platinum. The different levels represent the amount of medical costs a patient could expect their insurance to contribute: 60, 70, 80 or 90 percent. But within each tier there are dozens of plan designs that give buyers the choice of different premiums, deductibles and networks of doctors, among other things. And the options are different in each state. The A.C.A.’s target audience included both low-earning Americans — those too wealthy to qualify for Medicaid but too poor to afford commercial insurance — and those who could not buy insurance through an employer, either because they were self-employed or because their jobs for small companies didn’t offer coverage.

The research thus far suggests that the differences between plans offered through the A.C.A. and those offered by employers may be quite significant. A study in the policy journal Health Affairs found that out-of-pocket prescription costs were twice as high in a typical silver plan — the most popular choice — as they were in the average employer offering. In research conducted with the Robert Wood Johnson Foundation, Dr. Polsky found that 41 percent of silver plans offered a “narrow or very narrow” selection of doctors, meaning at best 25 percent of physicians in an area were included. The consulting firm Avalere Health found that exchange plans had 42 percent fewer cancer and cardiac specialists, compared with employer-provided coverage.

Some of the problems may have been predictable. When designing the new plans, for-profit insurers naturally tended to exclude high-cost, high-end hospitals with whom they had little clout to negotiate discounts. That means, for example, that as of late last year none of the plans available in New York had Memorial Sloan Kettering Cancer Center in their network — an absence that would be unacceptable to many New York-based employers buying policies for their employees. Another issue is out-of-state coverage, which many A.C.A. plans don’t offer aside from emergencies, and which is routinely offered in policies from companies — especially large ones — with workers in more than one state.

As a result, many parents who were excited that they would be able to keep their children on their policies until age 26 have discovered that this promise has gone unfulfilled. When Sara Hamilton of New York was shopping on the exchange for a plan to cover her and her two young-adult children — who live in distant states — she discovered that none of the plans covered doctor visits in those places.

And when Simon F. Haeder of the University of Wisconsin and his colleagues studied the plans sold on the California exchange, they found that they included 34 percent fewer hospitals than those sold on the open market and tended to exclude the priciest medical centers, like Cedars Sinai, a highly regarded hospital that runs the largest heart-transplant program in the country.

Plan size, of course, is not the only consideration. The research also showed that those limitations might not matter so much for patients’ health: The distance traveled and the quality of the providers was similar under both types of policies. He acknowledged, however, that California’s exchange, called Covered California, has higher standards for plans than others do, and those results may not be typical.