Mixed-ADC architectures are a promising solution to reduce power consumption in massive MIMO systems, yet their efficiency depends critically on the balance between one-bit and high-resolution ADCs. This paper develops a formal multi- objective framework to jointly analyze the trade-off between sum-rate and energy efficiency (EE). Through Pareto-front analysis, we identify a phenomenon termed Pareto Front Degeneration, observed in high-resolution configurations. Simulation results show that, at the knee points, the Mixed-ADC 1-vs-3 system (1-bit + 3-bit ADCs) achieves superior performance, with throughput gains of 5.5% over 1-vs-4 and 9.1% over 1-vs-5, together with nearly double the EE at high SNRs. These findings establish the 1-vs-3 configuration with a 40-50% mixing ratio as a practical operating point for energy-efficient massive MIMO design.