This paper shows that the signal-to-interference-plus-noise ratio (SINR) at a base station (BS) equipped with an arbitrary physical array antenna can be expressed as a function of two fundamental, stochastic figure of merits (FoMs): (I) the instantaneous effective gain (IEG) and (II) the beamforming-channel correlation (BCC). This result is achieved by applying a novel channel normalization approach using a reference array to preserve effects induced by the embedded element patterns of physical antenna elements. It is shown that both FoMs provide essential insights for quality-of-service (QoS)-based array antenna design by investigating their statistics for BSs applying full-digital (FD) zero forcing (ZF) beamforming. Various array designs are evaluated, and it is shown that arrays with higher IEGs and a reduced probability of low BCCs can increase the ergodic sum rate and reduce the need for scheduling. This paper shows that the signal-to-interference-plus-noise ratio at a base station equipped with an arbitrary physical array antenna can be expressed as a function of two fundamental figures-of-merit: (I) the instantaneous effective gain (IEG), and (II) the beamforming-channel correlation (BCC). Various array designs were evaluated and it is shown that arrays with higher IEGs and a reduced probability of low BCCs can increase the ergodic sum rate and reduce the need for scheduling.image