The difficult thing with this is it isn't like there was just 1 team. I mean the Durant years, the Warriors were better than they were with Barnes or Wiggins and the Spurs had the Robinson years and then the Parker/Manu years (and a very young Kawhi). This isn't the Celtics of the 80's where the Bird, McHale, and Parish were on every team (and I know that first title year Cedric and Tiny were more important than certainly McHale if not both Parish and McHale).
Comparing the teams at their absolute best I'd take the 17 Warriors (the best Durant team) vs. the 07 Spurs (Duncan was at his absolute apex prime)
Top 10 (with starters 1st)
Curry, Klay, Durant, Dray, Zaza, Iggy, Livingston, West, Clark, McCaw
vs.
Parker, Bowen, Finley, Duncan, Oberto, Manu, Horry, Elson, Barry, Vaughan
The question in that match-up comes down to how much can Draymond actually limit Duncan. I think the Bowen/Finley combination on Durant would do ok, and Manu/Parker vs. Curry/Klay wouldn't be a blowout for the Warriors. So it really comes down to that Draymond/Duncan matchup to me. If TD is able to be TD, then I think that would put the Spurs over the top, if Draymond limits TD, even just a pinch, then I'd favor the Warriors.