From your image, the *advancing* blades (right side) would indeed be faster (relative to the air). Which would produce more lift compared to the left *retreating* side.

This is called [dissymmetry of lift][1].

However, the blades are allowed to flap (change angle) independently from each other, to be able to counter this phenomenon.

>If this condition were allowed to exist, a helicopter with a counterclockwise main rotor blade rotation would roll to the left because of the difference in lift. In reality, the main rotor blades flap and feather automatically to equalize lift across the rotor disk. Articulated rotor systems, usually with three or more blades, incorporate a horizontal hinge (flapping hinge) to allow the individual rotor blades to move, or flap up and down as they rotate. A semi-rigid rotor system (two blades) utilizes a teetering hinge, which allows the blades to flap as a unit. When one blade flaps up, the other blade flaps down.

> [danubewings.com][2]

https://www.youtube.com/watch?v=Mx7vLB3KP1w


  [1]: https://en.wikipedia.org/wiki/Dissymmetry_of_lift
  [2]: http://www.danubewings.com/airflow-in-forward-flight-dissymmetry-of-lift/