Well, it is official -- now that the New York Times has taken note -- that there will be considerable variation among and between the states' essential health benefits in the small and individual group markets under the ACA mandated insurance exchanges. You can see the NYT's announcement here: http://www.nytimes.com/2012/12/06/health/interest-groups-push-to-fill-margins-of-health-coverage.html?_r=0.
Of course, this continued flowering of health care federalism was foretold months ago in the announcement by the Secretary of HHS that, although the language of the ACA reserved the definition of EHB to the secretary, this definition would be developed in consultation with the states. This decision to allow, even under the ACA, for geography to be destiny in healthcare was a weighty one and one, I would imagine, brokered under pressure from all sides.
First, it is likely those states who had relatively rich state specific insurance mandates, pre-ACA, would not want to have equalized downward to a less rich essential benefit. This is why, I suspect, November 26, 2012's announcement of a a notice of proposed rule making on EHBs grandfathers in state-mandated benefits enacted before December 31, 2011 as part of EHB without additional costs to the states.
Second, it is likely those states who had relatively thin state specific insurance mandates, pre-ACA, would not want to have equalized upward to a richer version of essential benefits both as a cost savings matter and as a philisophical position on the wisdom of comprehensive health insurance. Let's call this the problem of moral hazard.
Where does this leave us? The tailoring of state-mandated benefits to fit with EHB combined with the EHB's benchmarking rules -- essentially allowing a state to select a benchmark plan from between and among certain kinds of extant health plans offered within their state -- goes a long way towards ossifying or codifying some of the gaps in coverage between and among states.
I discuss some of the implications of health care federalism and the ACA in my draft paper: Let Fifty Flowers Bloom: Health Care Federalism After National Federation of Business vs. Sebelius (forthcoming UMKC L. Rev. 2012), which you can also find posted here on SSRN:
if you care to read more.