Disclaimer: I hold a small amount of stock (and lost a lot of market value) in a silicon-carbide gem company.
Yep - silicon carbide is very cool. It's weakly birefringent, which can be noticeable in larger gems, but the refractive index is larger than that of diamond, and the dispersion is greater too.
No matter from whence your gems come, the nuclei were largely forged at the heart of a star, same as everything but the hydrogen in your body.
The only people to whom I recommend natural stones are those with a connection to the earth or to a specific place. Geologists have a soft spot for natural diamonds. When considering an engagement ring for my now-wife, I spent a lot of time looking at sapphires from Montana. Only the risk of shattering them in a tension setting kept me from going that route.
The final thing that nudged me into synthetic stones was looking into the open-pit Cripple Creek gold mine. The environmental destruction we create in search of precious materials is considerable. Synthetic stones are made from carbon, sand, and electric power, all comparatively easy on the planet.
Diamonds are cool. So are lots of other choices. Look around; it's neat.