Horford is a fundamentals guy, plays the right way. So is Durant, and he wants to win. He doesn't care about being in ESPN as long as his team wins. You can have all the highlight dunks you want, but it doesn't win games at the end of the day.
Westbrook is a fun player, but he takes some really bad shots, could some of those have lost them games?
Plus you need a good inside out guy now, need some one to dumb it into to get a easy bucket, or to draw the D and kick it out for and outside shot. Or to pull the other teams bigs out so you can work in the paint.
Yeah he's not going to wow you with high flying dunks, but he'll be a good teammate.