who is better?

Just a sec. In the position of your last line. The one which goes

(14. a4g515. b5axb516. axb5g417. b6g318. b7g219. b8=Q g1=Q)

What makes you think this is a draw? It could possibly be a win for white, too. It's white's turn and he has a powerful pawn on c6. I'm not sure though, maybe you're right.

@aman_makhija, Consider that Q+N vs Q = draw, all black needs to do there is Rxc6 and he has a draw even if he lose the h-pawn. With that in mind I think white has no business entering that endgame position. Black has an h-pawn that could potentially be dangerous and if black is allowed to give checks with his rook and queen towards the white king that could be dangerous as well.

I haven't looked weather white can draw there, but it is beside the point since white could avoid this line by repeating the position earlier. I never claimed that position is a draw.

I'm talking about it from a practical aspect. If I had a choice I'd choose white. I know maybe theoretically it's a draw.

Trying to win practically with white there? What are you going to try to do? Try to promote the pawn without letting black sac the rook for the pawn? Hope black leaves the rook undefended at some point and fork the king and rook with the queen? Hope to win blacks queen with a knight fork at some point? It just sounds very very very unlikely to me, even from a practical perspective.

good point.

In your line, I'll support a2 and only then capture a6.

Ok, support it how? Black plays Rf3+ and takes the g pawn next most likely.

I would take Black in this position.  A Rook vs. Knight+2 pawns in an end game wins.  The fact that there are pawns on both sides of the board helps Black, since the Rook is much more mobile than the Knight.

I think FirebrandX has already given the right evaluation. White should be able to hold a draw, but white must be careful to not just let blacks rook dominate. You do not need to overanalyse the position to know that it should be a draw. I've tried to play against myself and I posted it in post #22 and #46 which both ended in draws (That was more for fun and my own interest rather than trying to find the truth of the position). 

Yep, but there are still some people here who think black has an easy win, like learning2mate. Unless someone blunders, the position is ultimately going to be a draw.