Why should black not capture the knight here?

Question

I played a game on lichess. (Link: http://en.lichess.org/n2hfBGYy#18) After the game I did a stockfish analysis of the game. This is the position:

[fen ""]
[Event "Rated game"]
[Site "http://lichess.org/n2hfBGYy"]
[Date "2015.03.09"]
[White "Kartikay"]
[Black "superca"]
[Result "0-1"]
[WhiteElo "1044"]
[BlackElo "1698"]
[PlyCount "56"]
[Variant "Standard"]
[TimeControl "300+6"]
[ECO "A42"]
[Opening "Sicilian Defense, Hyperaccelerated Fianchetto"]
[Annotator "lichess.org"]

1. e4 c5 2. Nf3 g6 3. d4 { Sicilian Defense, Hyperaccelerated Fianchetto } cxd4 4. Nxd4 Bg7 5. Nc3 Nc6 6. Nxc6 bxc6 7. Bc4 e6 8. O-O d5?! { (0.44 → 0.96) Inaccuracy. The best move was Qc7. } (8... Qc7 9. Bg5 Ne7 10. Re1 Rb8 11. Bb3 d6 12. Qd2 O-O 13. a3 Rd8 14. Rad1 Ba6 15. Bf4 Be5 16. Bxe5 dxe5) 9. exd5 cxd5 10. Bb5+? { (0.99 → -0.29) Mistake. The best move was Nxd5. } (10. Nxd5 Bb7 11. Bb5+ Kf8 12. Nf4 a6 13. Qxd8+ Rxd8 14. Be2 Bf6 15. Nd3 Kg7 16. Nc5 Bc6 17. Nxa6 Ne7 18. c3 Nd5 19. Bd2 Nc7) * {The rest of the game is not shown here}

I played 10. Bb5+ an stockfish labeled it as a mistake. Stockfish said that the best move was Nxd5. I was surprised by this, why should black not capture the knight in this position?

[fen "r1bqk1nr/p4pbp/4p1p1/3N4/2B5/8/PPP2PPP/R1BQ1RK1 b kq - 0 10"]

(Stockfish gives the evaluation +1.48 if black captures the knight.)

Answer 1

What comes to my mind (maybe someone can check with a computer):

After 10.Nxd5 ed 11.Bxd5 the rook is attacked and you have the motif of playing Bxf7+. The bishop cannot be taken because the king has to keep defending the queen. So after 11…Rb8 12.Bxf7 Ke7 you already have three pawns for the piece, i.e. material is equal and the black king has lost the right to castle and will come under attack. Possibly giving the exchange with 11…Be6 is better, but even then the intermediate check 12.Bb5 looks very nasty (After Bd7 there is always Re1+ as well and the maybe Bg5 ...).

Answer 2

If Black captures the knight, and you recapture with the B on d5, you "fork" the rook on a8 and the pawn on f7. Taking the latter leads to a strong attack (more on this in the next paragraph), so Black's best move is probably 11. ... Be6, protecting the f pawn and indirectly the rook, but allowing you to capture the rook. After Black recaptures with the Q, you have a rook and two pawns (one of them passed on the c file) for a Bishop and Knight. You also have superior development, and moves like 12. R e1 or 12. Qd6 or 12. c3 give Black a hard time. With your advantage in development, you should be able to transition into a favorable endgame with a dominant queenside, where the passed c pawn will win for you.

If Black rescues the rook with b8, you play B xf7+. Black can't capture without losing the queen so he plays Ke7. You play Re1+, Black is forced to play Be6. You play BxBe6+, with three extra pawns and a strong attack against an exposed king.