The Viper brand has 2 types of towels (that I know of).
There is the yellow (mine is, so I assume that they all are) Viper Glass Cleaning cloth that is for glass. The major difference is that this towel has fibers that are split on the end instead of looped, which leaves a micro bead of water behind that evaporates quickly. The key is to thoroughly wet the cloth and WRING, WRING, WRING until almost dry. This will clean the best.
The Viper Detailing cloth (mine are green) are for grunt work. They are not nearly as plush as the Miracle Towel, but are designed for polish/wax removal, and other types of grungy jobs (doorsills, etc.). They are built the same way as the Miracle Towel, where the fibers are looped, just not as plush.
So direct comparison of the Vipers to the Miracle Towel is not completely possible, as they are designed for different uses. But they are definitely members of the same family.
I hope that htis helps.