english opening botvinnik system question

I have a complicated question about the botvinnik system in the English opening. For move 11, should I go for a tactical shot like Bxh6 or Nxe5; or more positional style like a4 or Rab8? 

I would favor the a4 move because it gives white more space to work on the queenside, but the downside is that the b-pawn is backwards and will take a lot of moves to achieve a b4 break to open up the a and b files for white.

What would you suggest and why? Thanks :)

Botvinnik would never allow a line where 3...Bc5 equalized.

A nice video on the Botvinnik-English by FM Grant Szuveges is viewable here:

http://www.youtube.com/watch?v=TjEd-2J5e0Y&list=PLSClIVKbmGUcMqFQVICgYPuO_a7DtDkWy&index=5

I'm not sure about the move order here but I think you have to play 8.h3. The downside of Nf3 instead of Nge2 in this system is that Bg4 can be dangerous. After 9...Nd4 the pin on the knight can become a problem. Something like 10.Bxd4 ed 11.Nd5 Nxd5 12.cd f5 would be good for Black.

Maybe you can play 11.Nd5 in the game.

Actually 11. d4 looks best. 11...Bxf3 12. Bxf3 exd4 13. Bxd4 Nxd4 14. Qxd4 and White has a space advantage, Black's pieces are not well placed for the new pawn structure and his a pawn is en prise. However, White's dark squares are woefully weak and exchanging off your remaining knight for his bishop creates a good knight bad versues bad bishop situation.

You probably need to study the opening a bit better. As someone already pointed out, you should not have allowed 3...Bc5. Playing  Nf3 deprives yourself of the f4 advance. Leaving you with a post up by Nd5, which would have been stronger if his bishop was on e6 since then Nxd5 would result in a pawn fork. Expanding on the queenside with b4, which does not undermine anything here and the fairly atypical d4 break with a pawn structure that ussually arises via the Kings Indian and is a close relative of the Maroczy's bind.

I don't think ...Bc5 is the worst thing in the world. White can always stick a bishop on e3 if he's not comfortable with it. 

White's position after 3...Bc5 is probably not as bad as a quick glance at database stats would tell you. But, Black does stick his finger in the gapping hole at d4. Also Be3, Bxc5 and ...dxc5 firmly gives up the d4 square and leaves d3 as a lasting weakness.