Cubic zirconia -- "cubic crystalline form of zirconium dioxide (ZrO2"
Moissanite -- "originally referred to a rare mineral discovered by Henri Moissan having a chemical formula SiC and various crystalline polymorphs... synthesized in the laboratory and named silicon carbide (SiC)"
Would you choose an non-traditional gemstone over a diamond?
And would you try to pass it off as a diamond?
Moissanite Vs. Diamond (Squidoo)
Cubic zirconia vs Diamond (Diffen)
Moissanite vs. Diamond Nexus** (eHow)
** "...cubic zirconia that has been coated with a protective chemical substance to prevent clouding and increase durability"