Introduction to two distinctive classes of FMCW MIMO radar approaches to imaging radar. Their key advantages and disadvantages are analyzed. The first class of MIMO radar technique prioritizes simultaneous transmission MIMO for achieving robust range Doppler detection performance. The second class of MIMO radar technique prioritizes large uniform array digital beamforming capability for achieving low ambiguity in the angular domain. Performance tradeoffs in detection sensitivity, target dynamic range in range, Doppler, and angle domains, and angular resolution, are discussed. Analyses on the design constraints, suitable use cases, and limitations of the two classes of approaches are also provided.