With the CIELAB polar coordinates, one can achieve better results with colour variations, counter colours or colour transitions than with HSB, which is derived from RGB. This is shown by Reto Stauffer from the Institute for Statistics at the University of Innsbruck:
"In contrast to the (in)famous Red-Green-Blue colour space the HCL colour space provides perception-based properties which allows to design efficient colour schemes for technical graphics, but also for design applications."
The comprehensive website on the subject of HCL (the common name for HLC in the American-speaking world) contains, among other things, a "colour schemer" with which one can create convincing gradients and colour technical illustrations or geodata impressively.
