Diamonds must be cut to what are know as "Ideal Proportions" in order to create the spectacular balance of brilliance and fire - the "sparkle" you see when admiring an Ideal Cut diamond.
Most people want a beautiful diamond to show their love, prestige, or to mark a significant occasion. The only aspect of a diamond's quality and appeal that is not predetermined by nature is how a diamond is cut. It only makes sense that a diamond should be cut to show the ideal balance of brilliance, fire and scintillation -- The Ideal cut.
In the final analysis, the difference between color and clarity is so slight that it is difficult to judge and compare. But when comparing an Ideal cut diamond with an average cut diamond it becomes easy - the Ideal cut diamond will look better. Further, an Ideal cut diamond of any given color will look better than a normal diamond of a slightly higher color/clarity grade. In other words, the difference in cutting creates the beauty, while the color and clarity accentuate it. When it comes to size and carat weight, remember a heavier bigger diamond is not always better.