"Melonite" is a proprietary version of nitride. There are MANY types/versions of nitride. Typically, "Melonite" or anything labeled as QPQ nitride will have a textured/satin look to it, where as the cheaper/quicker versions of nitride (without the polish/quench done after the first treatment) will have the glossy (almost blued) black look.
Example: Faxon barrels look very much like Freedom melonite barrels (textured satin black), where Ptac nitride, RF nitride, and BA nitride all have the glossy black look. Either way will serve the same practical purpose, just different levels of attention/process.
I prefer the matte look of Freedom/Faxon, but have both types (glossy and satin) and they will serve you the same results. It's (basically) just a matter of esthetics (although manufacturers using the more extensive QPQ will argue otherwise).