Differential power processing (DPP) architectures employ distributed, low power processing, submodule-integrated converters to mitigate mismatches in photovoltaic (PV) power systems, while introducing no insertion losses. This paper evaluates the effects of the simple voltage-balancing DPP control approach on the submodule-level maximum power point (MPP) efficiency. It is shown that the submodule MPP efficiency of voltage-balancing DPP converters exceeds 98% in the presence of worst-case MPP voltage variations due to irradiance or temperature mismatches. Furthermore, the effects of reduced converter power rating in the isolated-port DPP architecture are investigated by long-term, high-granularity simulations of five representative PV system scenarios. For partially shaded systems, it is shown that the isolated-port DPP architecture offers about two times larger energy yield improvements compared to full power processing (FPP) module-level converters, and that it outperforms module-level FPP approaches even when the power rating of DPP converters is only 20-30% of the PV system peak power. In the cases of aging-related mismatches, more than 90% of the energy yield improvements are obtained with DPP converters rated at only 10% of the PV peak power.