Some thoughts on recent posts in this great thread:
In a single stud wall, increasing the stud spacing reduces contact area and increases the flex of the panel. The flex is the real key here. The mass of the framing material is not the key. 24" OC framing performs better than 16"
25 ga. steel studs are more flexible than wood studs, so they will always outperform a wood stud, although the spacing (contact area) is the same and the mass is less than for wood. 20 ga steel studs are much stiffer (like wood studs) and therefore the performance of wood stud vs. 20 ga steel stud is very similar. 2x6 steel studs are much stiffer and performance is limited. This is offset somewhat by the larger air cavity. 25 ga. steel studs perform better than wood studs or 20 ga steel.
None of the above examples are decoupled.
The conversation regarding framing material and spacing is all somewhat moot when looking at a decoupled framing such as staggered stud, double stud, resilient channel or resilient clips. In a decoupled framing scenario, wood studs and metal studs behave similarly, and in that instance the added mass of the wood studs would give a bit of an advantage.
The real mass effect is from the drywall or plywood, not the framing.
MLV (Acoustiblok) is simply more mass. Drywall is mass, plywood is mass, etc.
You can make a plywood / drywall sandwich on the studs if you want a nail base. Very common and practical, although there is a loss of mass vs. using drywall as Dana1 pointed out.