The quality of the cut of a diamond is important, because it dictates a diamond’s fire, sparkle and brilliance. A standard round brilliant cut will have 57 facets and how these facets relate to each other will determine how the light will pass through the diamond. The scale for the quality of the cut goes through Excellent, being the highest grade, Very good, Good, Fair or Poor.
As with colour, unless you have stones side by side of differing cut grades, it would be very difficult to tell an Excellent from a Very good cut.