If we play 15/3, 13/9 then 66, 65, and 55 force us to leave a shot. That would be a blunder.
The other two rolls allow us to play all our numbers without leaving a shot. 15/7, 13/5 means we'll have to leave a gap if we roll 55, but I think that it's worth risking that to avoid burying a checker on the ace. The two plays are probably quite close, but I think 15/7, 13/5 has the edge.