Moissanite is a nonporous stone, so it doesn’t get cloudy. It can get dirty on the surface like a diamond, but you can just rinse it off. On the other hand, a diamond will turn cloudy if it is in a house fire, while moissanite will not.
Naturally occurring moissanite is extremely rare, while naturally occurring diamond not so much. A geologist might judge you for wearing something that isn’t real moissanite but a knockoff with a lower refractive index.