you would have better defined scales/flakes in your model doing them your way (as long as your painted lines match the scales/flackes on your colour map) but they would to me end up looking like cubes with hard edges, desaturating the colour map will give you the nice smooth transitions on the bumps.

Maybe just try one then the other thne see what gives you the best result, you might end up using both by layering them in photoshop and adjusting the opacity, in the end its whatever works best.

As I said try rendering a quick test with one (desaturated) then the other (yours) and see what meets your requirement (oh and post the results so we can comment LOL)