Placing the bishops on the right square I have always been curious about how I can determine whether the bishop is better on e7 or on d6 playing with Black (of course when c5 and b4 are not possible or satisfactory).
I will provide some games of mine:


For instance, in this position the bishop has to retreat either to e7 or d6. The difference in the valoration is not huge but the bishop on e7 has a greater advantage for black (0.7) whereas on d6, where I think the bishop is more active as it controls the central square e5, the computer says Black only has an advantage of 0.4.

In this postion which is more similar to the point I am referring to, Black can choose both of the squares but putting the bishop on e7 is slightly better. 



All I want to know is what is the nuance between them that makes the assessment of the positon vary a little. I have provided these two games but I would really appreciate advices for ANY similar situation regarding the squares e7 and d6.
In both diagrams, the bishop is better on e7, because the d-file is likely to become an open file, and the bishop would block the rook's activity.

The first example has the future activity of the bishop to consider.  As the bishop isn't going to exchange on f4 or needed to protect an e5 push, its activity will have to come after moving to f6.  Here it will exert pressure on white's queen side.

The second example has breaking the pin as a consideration.  Without the bishop on e7, the queen would be tied to the defense of the f6-knight.  If the pin remained, Ne5 would be a strong move as the capture is now more dangerous--providing another attacker upon f6.

As a general rule, the more squares the bishop can attack on the opponent's half of the board, the more active it becomes.  However, especially as black, the more passively placed king's bishop is needed for other reasons, mostly defensive needs.