MartinC wrote on 04/22/11 at 12:38:51:
Actually checked the drawing rates on a database to make sure. (of TWICs and not huge.). ~28% for Nc6 and ~35% for Na6/ed/Nbd7.
Very similar overall scores, so thats the biggest difference. Not a huge one of course, because even the non Nc6 stuff is pretty unbalanced
But if the ....Nbd7 and ...Na6 lines are to be true "anti-drawishness" weapons, it depends on playing them on move 6 to avoid 6...e5 7.dxe5. So you really have to compare, for example, 6...Na6 7.0-0 e5 AND 6...Na6 7.Nd2!? with 6...e5 7.0-0 Nc6 AND 6...e5 7.dxe5 AND 6...e5 7.d5.
And it gets even more complicated, since both 6...Na6 and 6...Nbd7 reduce Black's options against the Gligoric 7.Be3 (but still leaves him with playable lines probably).
Matemax wrote on 04/22/11 at 12:12:20:
If the knigth is on a6 you can simply play ...c6 after:
1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nf3 0-0 6.Be2 e5 7.0-0 Na6 8.de5 de5 9.Qd8 Rd8 9.Bg5 c6 and I would rather be Black here: You can exploit the d4-square
If the knigth is on c6 then:
1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nf3 0-0 6.Be2 e5 7.0-0 Nc6 8.de5 de5 9.Qd8 Rd8 9.Bg5 and now you have to move the rook again due to the threat of Nd5 - of course Black is equal in the resulting position but with the Na6/c6 is perhaps slightly more equal than White
Lines with dxe5 on move 8 (after White has castled and Black has either ...Nc6, ...Nbd7 or ...Na6 already in) are considered completely toothless, maybe already better for Black. So that doesn't play any big part in deciding which line to choose.
6...Na6 7.0-0 e5 8.dxe5 is a possible order of course, but not something that should bother Black.