A diamond, whether it's mined lab grown is one of the hardest substances known to man. This means that they are extremely difficult to damage or scratch and therefore will maintain their sparkle for many generations.
Diamond stimulants such as moissanite or cubic zirconia are of inferior quality to our diamonds. They are not as beautiful and can easily be distinguished to the naked eye.
Diamond stimulants are not as hard as diamonds, which means they are likely to be damaged and scratch with daily wear.