Who would you play in this position and why?

I would castle and attack the A file, creating a semi open column, at the same time creating an outpost for my knight at B4.

Doesn't axb followed by Bx just win a pawn, open up the a file, give a protected passer, and enable the b pawn to be mobile? Maybe I'm missing something obvious, but black's position looks pretty nice there. On the other hand, I would avoid castling because Bxh7 stuff (with Nh5, Ng5, and Qh5, with the move orders all varying according to the tactics) looks scary with a pawn on e5 and no knight to help defend on the Kside. Staying in the center--at least for now--may be the safest bet.

So I take back what I said about Bx. Nx is better, threatening to eliminate the light squared bishop and leaving the B on e7 as a defender of g5. 

Edit: Just to be explicit, pawn pushes such as g6?! would create a weak color complex for black and give the potential for sacs on g6. Black might try Bf8, g6, Bg7, but that looks very slow while creating unnecessary weaknesses and his play should be on the Qside anyway.

Black all the way. Extra pawn for no compensation after axb4 cxb4 Nxb4.

Even if Black didn't have that extra pawn I'd still take Black because his plan is in far better "condition" than White's. Compare the status of White's kingside attack versus Black's queenside attack.

Thanks for the comments. True. Black was better. But Black didn't follow at all the queenside plan and after Nh5 g6, as akratic pointed out, my attack became real and strong. The game is not finished yet but its close. Here it is till the last move:

What's the correct move for Black after Nh5? Rg8 maybe? Do you think white's kingside attack before Nh5 was superficial after all? i'm not sure..

Before g6 i meant! sry! :)

I like the Petrosianic 14..Bf8 for Black.

For example 15. Ng5 b3 16. Bb1 h6 17. Nh7 Rxh7 18. Bxh7 Rxa2 and Black's pawns are worth a lot more than White's exchange.