[The HACK]

The benefit to a multi-piston FIXED caliper system is not the clamping force, since a properly engineered system SHOULD have roughly the same piston area as a stock system, otherwise your brake pedal would be all f**ked up. If the aftermarket system has a larger overall piston area than stock, the brake pedal would be soft/mushy feelie. If the aftermarket system has LESS piston area, the pedal would be ROCK HARD to press.

The benefit to a multi-piston caliper is two-fold. First, the same piston area is spread out onto multiple surfaces, thus allowing the engineers to build a system that spread out the forces applied evenly to prevent flex or twist in the brake pad. Second, a rigid, fixed caliper design has less flex. Both of which contribute to a more precise brake control and modulation compared to stock sliding caliper design. However, the pads must be longer in shape to accommodate the spread-out piston pattern, leading to a smaller sweep area.

Another "benefit" to a fixed style caliper is that since the mount is fixed and rigid, the caliper bodies can be constructed out of aluminum to save weight. Typical 4 or 6 pot calipers can weigh a few lbs lighter than the stock iron caliper since the bracketry required to mount a fixed caliper is much lighter and smaller.

Since brake rotors discs can only be made of iron or exotic material like ceramic composite for their heat dissipation properties and strength, a single piece rotor will weigh more than compound rotors. Compound or 2 piece rotors can have the hub area be constructed of a lighter material, typically aluminum, and saving quite a few lbs. especially custom constructed kits that uses a multi-piston fixed calipers, where the sweeping area is drastically reduced from the stock sliding caliper design, so the rotor rings can be constructed to be much shorter and the hub area increased to further reduce weight.

In addition, 2 piece rotors can be designed to separate the rotor disc away from the rotor hub. There are multiple benefits to this as well, a hub separated from the heat sink that is the iron rotor will prevent heat from being transferred directly to the wheel bearing, prolonging the life of the bearing in a race application. Additionally, separating the hub and the heat sink allows the rotor to expand and contract independently from heat to prevent stress cracks and warpage. Lastly, the physical separation of the disc and hub allows for an open area where the internal cooling vanes of a vented rotor to draw in more ambient air thus allowing for a more efficient cooling. The only drawback to 2 piece floating rotors is that they're very expensive to make.