4-piston calipers are good when everything is right, but if the rotor becomes a little warped, it creates problems with "knock-back" where the warped part of the rotor slams the pistons back into the bores of the calipers.
A floating caliper, on the other hand, has the ability to keep the piston/brake pad in contact with the rotor even it it's slightly warped, because the caliper can move back-and-forth on the caliper's anchor plate guides.
In the original K/H 4-piston calipers, there was lots of problems with the steel pistons seizing up in the caliper's bore. With the stainless steel replacement pistons though, this has pretty much eliminated that problem.
Both types of brake setups have their advantages/disadvantages. It just becomes a matter of preference what the individual prefers to use.