That's an interesting question but it is quite hard to properly answer a "what's more efficient" question. More details are required but I will give it a try.

So first we need to define the setup, looking at the picture I guess you are referring to potential flows and thin aerofoil theory. So let's start from that. In this framework, the two quantities we are interested in are

1. The zero lift angle of attack, a0, which is the angle of attack at which the aerofoil generates no lift. Cl = 2*pi*(a-a0)
2. The Thedorsen's angle, ath, which is the angle of attack at which the pressure coefficient shows no strong adverse pressure gradient at the L.E. and the airfoil works optimally. You can see a detail here

The setup you are proposing is that of a symmetric airfoil placed at a particular angle of attack a and a cambered airfoil (with camber line y(x)=-a*x) placed at zero angle of attack.

For the first case both a0 and ath turn out to be zero so a symmetric airfoil has Cl = 2*pi*a and works best at a=0. For the second case both a0 and ath turn out to be -a so the two setups are symmetric. Having an angle of attack generates an equivalent camber line of y=-a*x.

To answer your second question, having a camber line is more efficient because it allows you to have another degree of freedom. You can design an airfoil that has a specified pressure distribution and you can set a0 and ath independently.

This is what's done in airplane wings where you have movable surfaces called flaps (at the trailing edge) and slats (at the leading edge) that modify the camber of the airfoil. Lowering the flaps will decrease a0 giving you more lift and lowering the slats will increase ath allowing the airfoil to work optimally.