I'm okay with either Pop or Casey winning it, too, because they both have excellent claims for the award.
For this award in particular, I like to see it going to those teams who overachieved or had lesser talent on their roster. Pop is without a doubt an excellent coach, but he's also got a ridiculous amount of talent on that team. Casey's Raptors have more talent than us, but it's not by all that much combined.
I would also be okay with a Kerr/Walton mix for the award. They obviously have a ton of talent on that team, too, but they're legitimately going to be an all-time great regular season team, with an excellent chance at actually being the best regular season team of all-time (best record anyways). That deserves an award, especially Walton's part in the process.