Apparently there's more than one way to pull out, of Iraq.
Clinton's 60 day plan specifies that she will begin pulling troops out after 60 days in office, beginning a gradual troop reduction. Obama promises to begin immediate withdrawal of troops, withdrawing all combat troops within 16 months. 
That neither candidate has promised categorical, universal withdrawal from Iraq is, of course, pragmatic. Permanent US military bases have already been constructed. We will always have some presence in Iraq, like it or not. Regardless, the military cannot continue to function if our troop levels there remain at current levels. Even the Pentagon has acknowledged that prolonged wars in Iraq and Afghanistan have made the military dangerously unprepared for any future national crisis. There is no reason to maintain or re-up troop levels in Iraq, from a National Security standpoint. Both candidates demonstrate an understanding of this with their proposed policy towards Iraq. Obama's policy is strong because it enumerates the future levels of US presence, and eliminates the presence of combat brigades. Clinton's plan is strong because because the token of the "60 day" promise will stick in the minds of all concerned parties, forcing a universal reevaluation.