Warriors:
This is a no brainer for them. They need a good rim protector and rebounder. Kessler is top 5 (if not 3) at both. He is limited offensively and he doesn't space the floor. But if he would have then the Warriors wouldn't be able to get him.
He makes only 5M this years which make it possible to get him without breaking the current roster.
Jazz:
The atmosphere with Kessler and the front office is not great and it doesn't seem they are sure about giving him what he will be asking for
They are getting a good young player and 2 FRP which is more than fair.