I think it is fitting that New Hampshire is the only state to allow same sex marriage in all circumstances except if the couple’s state of domicile — where they reside and intend to continue to reside — forbids it. I can’t see that it benefits New Hampshire at all; it probably just makes it more costly to administer family law up there. But it strikes me as the flavor of live-and-let-live one would expect from the state.
Incidentally, the extant alternatives to New Hampshire’s regime are: (1) allow same sex marriage in-state and recognize all that are validly celebrated out-of-state (New York, Massachusetts); (2) disallow same sex marriage in-state but recognize all validly celebrated out-of-state (Rhode Island AG opinion); (3) disallow same sex marriage in-state and decline to recognize validly celebrated out-of-state same sex marriages (Texas). [Amusingly, the Texas case declining to recognize out-of-state same sex marriages was a divorce suit between two men whose Massachusetts marriage Texas, in effect, helped to preserve and sustain.]
One reasonable regime that, to my knowledge, is nowhere in force is the converse of New Hampshire’s: disallow same sex marriage in-state and recognizes all validly celebrated out-of-state same sex marriages except those celebrated by a domiciliary for the purpose of evading the in-state SSM prohibition.
A good overview of this and related subjects (including the implications of the Full Faith and Credit Clause for interstate recognition of same sex marriage, which I have discussed incompetently in the past) is here. Baude’s article is also excellent, as are many of its sources.