Who benefits? Who loses? Win/Win? Lose/lose? Both are franchise cornerstone players. One is Offensive firepower the other is Defensive identity. One the Golden Child the other the quiet invisible one. Both play in similar and well organised systems.
I searched for food when I read Curry and found this http://www.sbnation.com/lookit/2016/3/16/11244742/kawhi-leonard-wingstop-coupons-spurs
That has been the narrative of Kawhi but in these past few seasons his offensive game has really developed and show signs of being very efficient as well. I feel both players are comparable in value.
Curry is a A+ offensively and about a D+/C- defensively. Kawhi is an A+ defensively and probably a B+/A- offensively. Taking into account the Warriors and Spurs rosters...I think the Warriors benefit more from this swap.
But I think since defense, by its nature, is more team-oriented, being A+ on offense has more net impact than being A+ on defense.
I disagree with this mainly because in Curry's case, his skills are being 100% utilized in his Golden State surroundings. Golden State is probably the biggest "spacing threat" team ever seen in the NBA. Take any of those guys out of that synergy, and put them on another team, and they won't have the same space. Conversely, Kawhi will make a larger incremental difference in defense for them than Curry does on offense with so many other weapons.