Wet grinders are just small melangeurs. However, melangeurs purpose-made for chocolate were designed and built to process cocoa beans. Small wet-mill grinders used in making chocolate were designed to handle much softer materials (think cooked lentils) and to run for short periods of time (think less than thirty minutes).
"Real" chocolate melangeurs use much harder granite and are designed to run for hours at a time. There are also some very specific differences with respect to axle design that separate the two – wet grinders have a single axle, for example.
One thing they do share in common is that they are not conches. And they never will be conches. Despite what the manufacturers claim. Despite what chocolate makers claim. They are not conches. They may deliver some of the benefits of conching, but very inefficiently.
clay - http://www.thechocolatelife.com/clay/