To the bolded, I feel like positioning and reading the play gets a bit undervalued among many fans when they evaluate goaltenders. A goalie who had perfect reads and positioning sometimes get comments like "He didn't face any tough shots". He did, he just made them look easy.
And I think you can connect this to Reimer and the reason they brought Bernier and why Babcock made an early decision to use Bernier as the #1. As a coach, you want a structured game. You want the forwards to know what the D-men is going to do so that they can support them properly, and you want the D-men to know what the goaltenders will do so they can support them properly. Reimer has always been a bit of a chaotic goaltender. His positioning isn't great and his rebound control has been crap as well, which lends itself to chaotic situations that can break down that defensive structure that the coach want. He makes up for it with other qualities, but he can't undo the scrambling needed.
However, there are two points that needs to be considered with this. First, Reimer has gotten better at this. His rebound control is much better, and his positioning has taken steps as well. Second, having a style that lends itself to a structured defense is secondary to actual shot stopping performance. Reimer has outplayed Bernier easily so far this season, and that should always be the main factor.