What is a Moissanite?
Moissanite was first discovered in 1893 in a crater created by a meteorite that struck Earth. When Henri Moissan, French scientist and Nobel Prize winner, discovered it in Arizona he initially thought that he had stumbled upon microscopic particles of diamond. He took to chemistry and discovered that the crystal structures were made up of silicon carbide (SiC).

Is Moissanite natural?
Yes, and no. Moissanite was born in the stars and discovered on earth in a very small quantity. However, after years of trial and error, the process of synthesizing Moissanite was perfected. So, all Moissanite available today is lab-created.

Is Moissanite a fake diamond?
NO! Moissanite is not a fake diamond. Moissanite is a gemstone, just like diamond is also a gemstone, and ruby, emerald, sapphire, morganite, etc. Moissanite was born in the stars and brought to earth by a meteorite – it is definitely not a fake diamond.

Will my Moissanite scratch, chip or change colour?
No, Moissanite is the second hardest gemstone known to man. It is practically just as hard as a diamond and is a whopping 9.25 on the Mohs scale. To put it into perspective, it falls between diamond at 10 on the Mohs scale and Sapphire at 9; a masonry drill bit is 8.5. It won’t scratch, chip or change colour but for peace of mind, they come with a lifetime warranty directly from the supplier.

Moissanite vs. Diamond Characteristics

                                           Moissanite Diamond
Durability On the Mohs scale, moissanite scores a 9.25, a very good score that makes it one of the hardest substances on earth, and very suitable for everyday wear as an engagement ring. Diamonds are the hardest known mineral and receive a 10 on the Mohs Scale of Hardness. Because of this exceptional score, diamonds are very durable and ideal for everyday wear. This contributes to their popularity as engagement rings’ center gemstones.  
Brilliance Moissanites exhibit a different kind of brilliance than diamonds do, as their faceting pattern is different. The fiery, rainbow flashes emitted by moissanites are beloved by some, but others feel that moissanite’s heightened brilliance can create a “disco ball” effect, especially in sunlight. The bigger the moissanite, the more likely it is that the difference will be noticeable. Moissanite has a refractive index from 2.65 – 2.69, which is higher than a diamond. A different type of brilliance is what makes it possible to distinguish a moissanite from a diamond. Diamonds reflect light in three different ways. The white light reflected back is referred to as brilliance, while the rainbow of colors refracted through the diamond is referred to as dispersion. The surface sparkle of a diamond, known as scintillation, is a third type of diamond light return. The combination of these three gives diamonds their famous sparkle.  
Color While moissanites are labeled as “colorless”, the gems can still project a yellow or grayish hue in certain lights. Here again, the larger the moissanite, the more noticeable the color. A colorless diamond, whether natural or lab created, has a natural body color that contains no traces of yellow, brown, or grey, resulting in a dazzling, bright white appearance.  
Price For the same size from the top view, moissanites are dramatically lower in pricing than diamonds of that size. Moissanite gems typically vary in price only based on size and whether the stone is Premium or Super Premium. Natural diamonds and lab created diamond prices vary based on shape, carat, cut, color, and clarity. Lab created diamonds are more affordable than natural diamonds.  
Sourcing Because moissanites are lab created, they are an appealing option for those seeking an eco-conscious gemstone as they require no mining. We go above and beyond the current industry standards to offer both conflict free diamonds, as well as lab created diamonds that are ethically grown with minimal environmental impact.  

Excerpt from www.brilliantearth.com

So which one should I choose?
The decision lies in your hands and is based on the end goal with your engagement ring design. Is there a specific look you want to go for, but can’t carve out hundreds of thousands for a huge diamond? Or would you rather have something extremely rare like a natural diamond and settle for a smaller version? It is your personal decision as one is no better than the other. Always remember: beauty is in the eye of the beholder and the value of a gemstone is only as much as you are willing it pay for it.