In this paper, we discuss the advantages and limitations of coherent multiple-input multiple-output (MIMO) radars. This is a radar system in which the transmit and receive elements are in relative close proximity so that the target response is coherent between transmit and receive antenna pairings up to a known geometric effect. In particular, we compare the performance of MIMO radars that employ a pairing of sparse and filled arrays for receive and transmit with a system given the same geometry that employs a nonadaptive, coherent transmit array, which we denote a single-input multiple-output (SIMO) radar. We show that MIMO radar provides a noticeable improvement, particularly for ground moving target indicator (GMTI) radars. This improvement is for target detection and estimation performance for an ideal system. We also address the performance benefits of MIMO systems in the presence of radar calibration errors. In addition, we show that in addressing issues associated with a SIMO radar, a MIMO radar is constructed.