I think a big factor is whether Durant wants to be a true #1 option, or more part of a team. In Boston, he's the clear #1, even though we play team ball today. In GS, Curry replaces Westbrook and it's more of a 2-header monster. In SA his numbers probably drop the most, with fewer minutes and the most extreme team ball. Aldridge and Leonard together would severely cut his usage.
Ideally for us, he wants to go somewhere where he can score 25-30/night as the go-to guy with a really, really good supporting cast, but he's still the undisputed star. We could be champs with a defensive center, Durant, and something close to the current cast.
Formula would be something like top-5 defense + top-5 scorer (Durant) + top-5 coach + great depth = winning.