There's no difference in their ability to propagate. One handedness doesn't work
better than the other, unless it happens to be paired with the opposite polarization
antenna in which case the pair doesn't work together at all. There are many ways
to describe and/or visualize what CP itself represents.
I'd refer you here, http://en.wikipedia.org/wiki/Circular_polarization
Bit of trivia. RealD 3D glasses that you use in a regular movie theater
use circularly polarized light. The movie projector projects images for both left and right eyes
onto the screen simultaneously, each side left and right circularly polarized.
The 3D glasses have left and right circularly polarized filters (unlike conventional
sunglasses which have vertical polarization). The left hand polarized light is
blocked by the right hand polarized lens, and vise versa, so each eye only
sees its own side's image. Because it's circularly polarized you can tilt
your head without a change in what each eye sees, same as CP antennas
can tilt with respect to each other and the magnitude of the signal received