re: Why is Les Miles so much more successful against Auburn than Saban?

Not sure you really want a legit discussion or not, but I think there could be a few reasons:

Bounce of the ball in close games (doesn't necessarily have to do with Saban versus Miles, more of an anomoly that can produce seemingly surprising results when you carve out particular data sets). Sometimes you have good/bad days, sometimes the other team has good/bad days.

Saban took on two rebuilding projects during this time period

Intensity of Alabama - Auburn rivalry (I feel like one of Saban's attributes is to build a pretty steady workmanlike team that usually have very successful seasons but sometimes I don't think they always match the extra intensity of the other side in big rivalry games)

Saban's relative struggle against the HUNH / spread teams / mobile QBs (really would just apply to the 2013 loss mostly, maybe 2010)