...Be7 or ...Bd6?

Hello everyone, 

Studying openings with engines and Chessbase I am puzzled why ...Be7 is sometimes favored over ...Bd6, and why it is sometimes the other way around. In some instances, it is obvious why, but often I don't see why one of these two moves would be better than the other. Can anyone please offer any general principles to help determine which of these two moves are better in a given position? 

Thanks in advance, 

Stefan

Here is an example. ...Be7 or ...Bd6 now? And why? 

And what about here? 

...Be7 or ...Bd6? And again, why? Your explanations are much appreciated.  

I hope someone can cast some light on this. Thanks.  

Thank you, both. I appreciate your replies. Still, what I am really after is some general principles which can guide me - and others - choose between these two moves. They sometimes seem equally good to me and still, the engines and Chessbase indicates that one move is significantly better than the other. 

I'd play ...Be7 there, just to prevent a potentially annoying pin of the f6 knight if white plays Bg5.

...Be7 in the second example is a must, because of a Nf5 response to ...Bd6

As a general rule (when in doubt), ...Be7 is often safer, and also referred to as the "Classical" way to develop the bishop.

...Bd6 has its place, too, though. Don't be afraid to try it out. Just know that it sometimes runs into tactics from White (especially those involving pawn exchanges or pawn advances in the center.)

Great! Thanks a lot, people! I understand the specific position is what truly matters, but the general principles you guys have given helps me a lot. Much appreciated!