Have made this http://www.babylonjs-playground.com/#20OAV9#20 trying to understand the whys and wherefores of the four coordinatesMode(s). You can see the differences as you rotate the camera.
Some obvious differences are PROJECTION_MODE uses part of the whole image, PLANAR_MODE uses the image repeated 4 times, CUBIC_MODE repeats of the image depend on the size of the image, SPHERICAL_MODE works best on spheres (surprise surprise).
Question when would you use each mode and why?