Does moissanite come with a certificate?

The difference is massive. Cubic zirconia is 8 on Mohs, scratches in months, and looks flat. Moissanite is 9.25, basically as hard as diamond, and has real fire. A CZ ring is a 20 dollar disposable. A moissanite ring is a 500 dollar piece you can wear every day for years. Do not compare them.

A 1ct moissanite looks slightly LARGER than a 1ct diamond because moissanite is less dense. A 6.5mm 1ct diamond is about the same visual size as a 6.5-7mm moissanite. In practice the difference is tiny but moissanite wins slightly on face-up size.

One thing nobody tells you: moissanite can get a hazy look if you use an ultrasonic cleaner on a poor-quality stone. Stick to warm soapy water and you will be fine.