I'm sure it's just a matter of taste--10 ... Nbd7 is one of Smyslov's ideas and isn't much less common than 10 ... Bxc5, but it has the advantage of preventing 11 Ne5, which helps to free up White's position.  I think Black gets some initiative for the pawn after 10 ... Nbd7, when White has some difficulty developing his/her knight at g1.  Nothing wrong with 10 ... Bxc5, of course; I just found 10 ... Nbd7 intriguing.  Road less traveled, etc.   

I'm less concerned about the pawn, and more interested in identifying a good plan for Black after 15 Kf1.  I've also been looking at: 15 Kf1 Bg7 16 h4 g4 17 Ne1 h5 18 Bb5 Nc3 19 Bxc3 Qxc3 but I'm not sure this is any good for Black.  My instinct is that 18 ... axb4 19 axb4 0-0 is the better option.  Is 18 ... 0-0, maintaining the tension on the queenside okay?

I was hoping list members might be able to help me make sense of a line in the pawn sac variation of the 5 Bc4 Smyslov Caro-Kann.

After 1 e4 c6 2 d4 d5 3 Nc3 dxe4 4 Nxe4 Nd7 5 Bc4 Ngf6 6 Ng5 e6 7 Qe2 Nb6 8 Bd3 h6 9 N5f3 c5 10 dxc5 Nbd7 11 b4 Nd5 12 Bd2 Qf6 13 Rb1 a5 14 a3 g5 the recommended line tends to be 15 Be4 Nc3 16 Bxc3 Qxc3+ 17 Qd2 Qxa3 and a complicated game with chances for both sides, where Black often exchanges his/her queen for a rook, piece, and pawn(s).  But has 15 Kf1 been played?  Hiarcs wants to play that move, and it looks rather interesting: 15 Kf1 Bg7 16 h4 g4 17 Ne1 h5 18 Bb5  In the 15 Be4 line, Black is happy to get White's light-squared bishop off the a6-f1 diagonal to avoid this pin.  With that in mind, 15 Be4 seems rather forcing and plays to Black's interests.  15 Kf1 removes the threat of the queen check from c3, and asks Black to initiate a new plan.  Presumably, developing with Bg7 isn't a bad idea.  15 Kf1 Bg7 16 h4 g4 17 Ne1 h5 18 Bb5 axb4 19 axb4 0-0 looks better for White.

Thoughts?