When used in a framed structure, any benefit created by mass loaded vinyl is not from the actual mass itself. The structure already weighs several pounds per square foot more than the MLV. To increase isolation considerably with mass alone, the material would need to double the structure weight.
What MLV brings to the assembly is a material that resonates like no other building material. Every structure or material has a resonance point. Including mass loaded vinyl in the structure will resolve many resonance issues allowing consistent performance in mid to high frequencies.
However, using different thicknesses of materials for drywall or wood layers, or the inclusion of Green Glue Compound between layers, will also resolve these common resonance issues.