  In this work, we study the achievable rate and the energy efficiency of
Analog, Hybrid and Digital Combining (AC, HC and DC) for millimeter wave (mmW)
receivers. We take into account the power consumption of all receiver
components, not just Analog-to-Digital Converters (ADC), determine some
practical limitations of beamforming in each architecture, and develop
performance analysis charts that enable comparison of different receivers
simultaneously in terms of two metrics, namely, Spectral Efficiency (SE) and
Energy Efficiency (EE). We present a multi-objective utility optimization
interpretation to find the best SE-EE weighted trade-off among AC, DC and HC
schemes. We consider an Additive Quantization Noise Model (AQNM) to evaluate
the achievable rates with low resolution ADCs. Our analysis shows that AC is
only advantageous if the channel rank is strictly one, the link has very low
SNR, or there is a very stringent low power constraint at the receiver.
Otherwise, we show that the usual claim that DC requires the highest power is
not universally valid. Rather, either DC or HC alternatively result in the
better SE vs EE trade-off depending strongly on the considered power
consumption characteristic values for each component of the mmW receiver.
