The “best cores” as defined by Ryzen Master corresponds to the electrical characteristics of the cores which are determined during the binning and testing phase of the chips at the factory. The physical and electrical characteristic data is fused on each chip, and is interpreted by the SMU firmware to create the ranking between the cores independent of other factors, and this ranking is what’s currently being reported by Ryzen Master as well as third-party application readouts out through the custom API.
The ranking of the “preferred cores” as characterized by CPPC2 does not directly correspond to the electrical characteristics of the cores, and further takes into account many other factors of the chip layout. The biggest factor at hand here that affects the choice of the highest performing preferred cores in the system, is that AMD is aiming to accommodate Windows’ scheduler core rotation policy.