This work presents a modelling framework to enable comparison and trade-off study of different aircraft system architectures. The framework integrates a computational module to select feasible architectures with a modelling platform that simulates the power generation, distribution and fuel consumption of the aircraft as well as system-level models for the system being evaluated. Its capabilities are demonstrated for the case of the electrification of the primary flight control system (PFCS) using different electric technologies (EHA, EMA) and different levels of electrification ranging from the conventional hydraulic to the all-electric. The performances of different architectures are analysed with respect to the change in the mechanical power extracted from the engine, the weight and the fuel burn of the aircraft. The framework demonstrates the capability of evaluating multiple, different, system architectures in a way that is scalable for different systems or different aircraft. It supports a designer evaluating the aircraft-level impact of their design choice at system-level, and it can aid in assessing technology options early in the design process.