Seeing stones in person is good, but if you order and return more than one stone there will be a small restocking fee.

First things first:

Asha is CZ with a diamond coating.
Diamond Nexus Labs is just CZ. Plain and simple. No matter what they advertise.
WinkCZ is also CZ but with expert cutting done.
Moissanite is moissanite. It's its own gem the same way CZ is a gem.

Gemesis Labs and BTD both grow real diamonds, but they generally match the prices that mined diamonds cost, so it's not really cheaper to go the man-made route, diamond-wise...

With lots of dirt/oil, CZ and Asha can lose their sparkle, but that's what cleaners are for! : )

Moissanite is super-fiery, so if you love color, go this route. They also tend to be a little warmer in color than CZ, so if you want to pass this off as a diamond, it'd be a little easier because it doesn't look absolutely WHITE. It's also much more durable than CZ. So this will last a while, though Asha can, too, if you treat it well.

If you want perfect-diamond white, go Asha; WinkCZ also would do nicely.

Don't go for Diamond Nexus Labs. They falsely advertise and sell plain CZ. Independent tests prove this.

Hope others can chime in on this!