Why is 8. Be7 like +1.2 and 8. Bc5 -0.6 here? (Blacks move) (1100 elo)

I mean i know that my experience is of course just not enough to understand those positional things. But that's why I am asking, maybe someone can explain that? Happy to read your answers

Edit: Ok, I understsood that you may want to deny white pushing the center pawns but there must be something else, doesn't it? I mean a difference of ~1.8... That's a half piece!

The bishop on c5:

Controls more squares.

Controls the center square d4.

Prepares to castle.

Keeps whites bishop off of e3.

Pressures f2.

The bishop on e7 develops, and prevents a pin.

I think Bc5 is better than Be7 personally

I had mistaken the e7 square for being the d6 square, and was very dubious (what with the knight winning a tempo). 

Well.......what exactly does Be7 do? (other than prepare castles, which both moves do)

In the position you give, White clearly wants to play d4 to undermine Black's centre, as @AnthonyAtanasov said. 

Also, after 8...Be7 9.d4,

purely from a pawn structure point of view, White is better because Black has an IQP (Isolated Queen's Pawn) that is blockaded. If you think just a few moves ahead, you can see that White is at least a bit better.

Bc5, on the other hand, prevents d4. This is called prophylaxis -- when you prevent your opponent's idea. Now, compare the positions after 8...Bc5 and after the variation with 8...Be7

Be7 -- 

Bc5 -- 

Well, which do you prefer? As you can see after Bc5, White cannot play d4 which just leaves Black with better placed pieces and much more space in the centre. Be7 just leaves Black with a worse pawn structure.

Droidfish on 5 men Tablebase with contempt 0 analysis.

As you can see in the first picture, Be7 allow d4!!

After d4, 1.  dxe4 lead to isolated pawn on d5, and

2. e5 lead to backward pawn on d5 .In both lines white has good positional compensation.

I followed the principal variation of droidfish in both lines for another 10- 15 moves.

8. ....Be7

8. ... Bc5.

I could not find any forcing lines where one side  lose/ gain one pawn.

Both lines gradually become close to 0.00 lately. Probably both lines are equal which leads to draw. But 8......Bc5 create better position for black that can lead better chance of winning in case white make mistake. ( To make mistake to opponent, you must make pressure to him/ difficult situation to him).

@drmrboss, that is a very good analysis, but I just don't think it's the type of position where we need to look at multiple computer lines........it's more about understanding the positional concepts.