...your making it sound like the heavier the rotating assembly, the more torque it will have.

torque is created by the energy made during combustion. rotating assemblies are balanced down to just a few grams, or should be anyways. there is no benefit from having an unbalanced/overweight rotating assembly.

what your talking about with the clutch dumping has to do with inertia. its already spinning and your trying to grab hold with the clutch. HP doesnt really play any part in that...a 40hp and a 4000hp engine can both spin 5000rpm with little load. now if there is alot of mass turning at 5000rpm then yes it will get you out with a bit more umph as there is more transference of energy, but the extra rotational mass isnt going to net you better power gains. it will take more power to turn it. usually rotational mass can be given a ratio of ~8:1 in comparison to regular mass (i.e. interior, seats, dash etc). this is why you may notice people gaining/losing up to 1.5-2 tenths in the 1/4 mile just by going to a new rim/tire combination