There is a divisive issue at hand - regular season vs. post-season.
Pop is a better regular season coach than Doc. It's close, as both are top-3 in the league, but Pop consistently gets more out of his players, including lesser players, than Doc does. Just last night Pop coached a B-squad to a 5-point loss against the Heat. Our A-squad has been blown out by the Heat, Spurs, Nets, and Pistons.
Doc spends the entire season getting all his players to buy into his team concept and their roles within it. When he accomplishes this goal (2008, 2009, 2010, 2012), he becomes the league's best post-season coach, bar none. When he doesn't accomplish this goal (2011), he's still a great coach, but the team doesn't stand a chance at winning the title. Doc sacrifices the regular season to build for the post-season.
Pop does a similar thing, mostly by outright resting players here and there (like last night), but in the playoffs the Spurs are nowhere near as dangerous or disciplined as they are in the regular season, no matter how rested their stars are.
If you care about regular season records, go with Pop and the Spurs. If the post-season and recent championship appearances are your thing, go with Doc.
The other issue is KG versus TD. The differences between them are astronomical, yet their similarities will place each in the HOF someday. I would love to read a book that discusses the careers of each in the same dialogue. I believe Duncan is the slightly better all-around player, but I love the intense and tenacious KG more as a player (and a Celtic). I'm sure I'd feel different if the Celtics had correctly won the 1997 draft rights to Timmy D.