CZ is a very satisfactory diamond simulant. A $10 CZ is almost impossible to distinguish visually from a $10,000 diamond - unless you're a very skilled grader, you really can't tell the difference without a thermal tester or a refractometer. The visual giveaway is that it's too good - the stones are perfectly clear, perfectly colourless and have exceptional fire. CZ grades better than the very best diamonds. When it was introduced in the 1970s, it sent shockwaves through the gem trade.

CZ is a bit less durable than diamond (8 vs 10 mohs hardness, some porosity), but it's so cheap that you can have the stone replaced if it starts to show signs of wear.

Moissanite is a very fine simulant, but to my mind, the main advantage over CZ is that it's more expensive. CZ is implausibly cheap for a high-quality diamond simulant.