Mono has no friction between the leafs. It only flexes, no friction. Rides better too. Anytime a design can be a mono, they use it. Cheaper too.
But the axle isn't well located in an F-body and the monos can deflect too much with hp. Install a radius rod or some aftermarket bars and monos should work OK with hp.
From a design perspective, which involves modeling and simulation of the components of the system, one desires the spring to provide *only* a spring constant, and the shock to provide the damping action. That allows fine tuning of the components for the best combination of ride and handling. Because of the friction between the sliding springs of a multileaf spring, the spring also contributes to the damping (in spite of the efforts to reduce that friction thru use of the plastic slides). The frictional component of the spring adversely affects the design of the total 'spring mass damping system'. The multiple leaves are a 'fix' for a different problem which popped up, or to support larger masses, or other issues. Ideally, the designer desires the spring constant, K, to be 'constant' thru the full range of operation as he does the damping action.http://www.acs.psu.edu/drussell/Demos/SHO/damp.html