  Analog Beamsteering (ABS) has emerged as a low complexity, power efficient
solution for MillimeterWave (mmWave) massive Multiple Input Multiple Output
(MIMO) systems. Moreover, driven by the low spatial correlation between the
User Terminals (UTs) with high number of transmit antennas (massive MIMO) at
the Base Station (BS), ABS can be used to support Multi User (MU) MIMO
scenarios instead of digital or Hybrid Beamforming (HBF). However, we show in
this paper, that even with high number of transmit antennas, the HBF can
achieve better Spectral Efficiency (SE) compared to the MU ABS even in pure
Line of Sight (LoS) channels. Moreover, we prove that the MU ABS saturates to a
constant SE at high transmit Signal to Noise Ratio (SNR) and we theoretically
derive an approximation to that saturation bound in this paper. On the other
hand, we highlight that the HBF's SE scales with the transmit SNR even in high
SNR regime. Finally, given the same power consumption and hardware complexity
as the MU ABS case, we show that HBF asymptotically achieves the optimal SE
(ideal non interference scenario) when increasing the number of transmit
antennas.
