Basically, all unions, heterosexual or same-sex, should be considered "civil unions" at the legal level (where it is a form of contract law). Religious organizations and individuals can decide for themselves whether to consider such unions to be "marriages."If you consider the separation of Church and State it is logical for Federal/State government to recognize civil unions thus reserving marriages to be performed by church officials as each denomination decides.
The larger issue, though, is the Defense of Marriage Act. None of these state-level acts, whether called marriage or civil union, will result in equal benefits until that law is repealed.