I can honestly say it is not even close: access to health care via ACA saves more lives every year than the population of Gitmo by nearly two orders of magnitude.[1]
And it's not clear at all that Obama could have successfully closed Gitmo even had it been a higher priority of his. It is clear that he immediately ended interrogative torture [2] and made efforts to close it. There's still force feeding but that's also an issue in us prisons so closing gitmo and sending the detainees to other prisons is not necessarily solving anything there.
[1] one early study here: http://www.latimes.com/business/hiltzik/la-fi-mh-obamacare-w...