Bi-polar ionization is the of the most effective technologies for air decontamination. Since the ions generated with the system will be passed along within the airstream, the effectiveness to reduce certain pathogens can be very effective.
Installing both UV and Ionization systems in a single system has no significant downside other than the additional costs. Both can work independently and they will not counter the effectiveness of the other. Both technologies have similar effect on viral, bacteria and fungus organisms.
UV-C systems are most effective for surface decontamination. A short period of time of exposure to the UV-C light to improve effectiveness is needed, so constant exposure of a cooling coil or drain pan in an AHU system will be the best benefit. The engineered solution for UV-C includes the analysis of coil dimensions, the thickness of a coil so that UV-C light can penetrate the depth of the coil and proper UV irradiance levels to all surfaces are obtained.
Overall, both systems have varying effectiveness depending on the contaminant. Both systems have been tested in national laboratories with published results. Neither solution have 100% guaranteed results, but both have success in reducing various particulates, pathogens and other VOCs.