Battle of Champions: 2012 Heat vs 2014 Spurs vs 2015 Warriors. Who wins?

I've thought the 2012 Heat team that won was better than the 2013 Heat team (though Lebron was at his Heat peak in the 2013 series). And the 2014 Spurs were better than the 2013 Spurs that lost in the Finals.

Given the similarity in play between the 2014 Spurs and 2015 Warriors (lots of ball movement, great 3PT%s), and the sheer firepower of the 2012 Heat, all three teams are pretty strong.

Even being a huge Lebron fan, I'd probably have to go with the 2014 Spurs, with their combination of shooting, play-making and defense.