The sectored multi-probe anechoic chamber (MPAC) is regarded as a promising millimeter-wave (mmWave) over-the-air (OTA) testing solution. However, there are still debates in the literature about which channel emulation method, i.e., pre-faded synthesis (PFS) or plane wave synthesis (PWS), should be used for the sectored MPAC testing system. In this paper, a thorough comparison between the two channel emulation methods is conducted. It is found that for sectored MPAC (where the active probes are unlikely to be uniformly distributed over the probe panel) the PWS is more accurate than the PFS in line-of-sight (LOS) scenarios and less accurate than the PFS in non-LOS (NLOS) scenarios. Explanations are given.Index Terms-millimeter-wave (mmWave), multi-probe anechoic chamber (MPAC), over-the-air (OTA), plane wave synthesis (PWS), pre-faded synthesis (PFS)