GMTonyKosten wrote on 07/12/10 at 18:16:58:
All the lines in the Symmetrical where Black plays ...Bxc3 are double-edged, at best.
I used to think so too, but this line might be an exception. It should at least be better than the similar 5.e3 Bxc3 6.bxc3 b6 because White's a3 has less value than Black's b6.
So far Black scored well and the very few wins for White I found unconvincing. Here are the three games I gave a deeper look when I had to answer 5...b6 in a correspondence game last year.
[Event "TCh-FRA Top 16 Gp B"]
[Site "Montpellier FRA"]
[Date "2008.??.??"]
[White "Gurevich,M"]
[Black "Schlosser,P"]
[Result "1-0"]
[WhiteElo "2607"]
[BlackElo "2564"]
[ECO "A30"]
[Round "4"]
1. c4 c5 2. g3 g6 3. Bg2 Bg7 4. Nc3 Nc6 5. a3 b6 6. e3 Bxc3 7. bxc3 Bb7
8. e4 d6 9. d3 Qd7 10. Ne2 O-O-O 11. Nf4 e6 12. O-O Na5 13. Re1 Kb8 14. a4 h6
15. Re2 g5 16. Nh5 f5 17. exf5 Bxg2 18. Kxg2 exf5 19. Re1 Qf7 20. d4 Ne7 21. d5 Rhe8
22. h4 gxh4 23. Re6 Ng8 24. Qe2 Nxc4 25. Nf4 Ne5 26. a5 Qb7 27. axb6 axb6 28. c4 Rxe6
29. Nxe6 Re8 30. f3 Nf6 31. Bf4 Nfd7 32. Ng7 Rf8 33. Qc2 hxg3 34. Nxf5 Nxc4 35. Qxc4 Rxf5
36. Bxd6+ Kc8 37. Qe4 1-0
Guru was a bit lucky IMO. I view 20.d4!? as an attempt to mix things up from a suspicious position.
[Event "Open"]
[Site "Ashdod ISR"]
[Date "2004.??.??"]
[White "Rechlis,G"]
[Black "Psakhis,L"]
[Result "1/2-1/2"]
[WhiteElo "2515"]
[BlackElo "2545"]
[ECO "A34"]
[Round "4"]
1. c4 c5 2. Nc3 g6 3. g3 Bg7 4. Bg2 Nc6 5. a3 b6 6. e3 Bxc3 7. bxc3 Bb7
8. d3 d6 9. Ne2 Qd7 10. e4 e6 11. h4 h6 12. Be3 O-O-O 13. O-O Kb8 14. Qc2 Rh7
15. Rfd1 e5 16. Nc1 Na5 17. Nb3 Qa4 18. Nd4 Qxc2 19. Nxc2 f5 20. f3 Nf6 21. Bf2 f4
22. g4 g5 23. h5 Bc8 24. Ne1 Bd7 25. a4 Rg8 26. Ra2 Rf7 27. Bf1 Be6 28. Be2 Rb7
29. Rb1 Rc7 30. Nc2 Bd7 31. Bd1 1/2-1/2
This game really depressed me.
[Event "Bundesliga 1999-2000"]
[Site "Luebeck GER"]
[Date "2000.??.??"]
[White "Thiede,L"]
[Black "Reeh,O"]
[Result "0-1"]
[WhiteElo "2390"]
[BlackElo "2399"]
[ECO "A00"]
[Round "11"]
1. g3 c5 2. c4 g6 3. Bg2 Bg7 4. Nc3 Nc6 5. a3 b6 6. e3 Bxc3 7. bxc3 Bb7
8. Ne2 d6 9. d3 Qd7 10. Nf4 e6 11. h4 O-O-O 12. e4 Kb8 13. O-O Nge7 14. Bh3 Qc7
15. Qe2 Bc8 16. Re1 h6 17. Bg2 g5 18. hxg5 hxg5 19. Nd5 exd5 20. exd5 Ne5 21. d4 f6
22. dxe5 dxe5 23. a4 a5 24. Rb1 Ka7 25. Bxg5 fxg5 26. Qxe5 Qxe5 27. Rxe5 Nf5 28. Be4 Nd6
29. Bd3 g4 30. Rbe1 Rde8 31. Re7+ Kb8 32. Kg2 Rxe7 33. Rxe7 Rf8 34. Rg7 Rf7 35. Rg6 Kc7
36. Be2 Bf5 37. Rh6 Bd7 38. Kg1 Rg7 39. Rh4 Ne4 40. Bd3 Nd6 41. Be2 Bxa4 42. Bxg4 Bb3
43. Be2 a4 44. Kg2 a3 45. Rh1 a2 46. Ra1 Nxc4 47. Bd1 Bxd1 48. Rxa2 Kd6 49. Ra8 Kxd5
50. f3 b5 51. Kf2 Nd6 52. g4 Rf7 0-1
White did not find a good plan and apparently he also failed to find something post mortem. In later games against Reeh (2003) and Andersson (2005) he chose the modest 7.dxc3.