Even uncut diamond crystals have a very particular "fatty" shine to it that some people might like and enjoy.
However I've seen demands that a fiancé purchase a real diamond, not a much cheaper "synthetic" one, even though it's structurally identical. That this was even a notion affirmed my assumption that the psychological importance of purchasing a diamond is tied to the price itself.
Luckily we dodged that bullet.
Whenever my wife gets comments about her moissanite, people notice it's different. Due to it's refractive index, it breaks light more and leads to a lot more colors seen when reflected back out of the stone. Loads of people just think it's a fancy diamond though since they don't know anything else and it otherwise looks very diamond like.
CZ will look about the same as diamond just not as sparkly on day one. But it's way softer, so if it's a daily wear it'll get all scratched up within several years. After 10 years of wear the difference between CZ and diamond is pretty clear.