In this paper, various inverter topologies are compared for integrated modular motor drive (IMMD) applications. Two-level voltage source inverter (2L-VSI), three level voltage source inverter (3L-VSI) and series/parallel combinations of these topologies with system level modularity are compared in terms of voltage and current harmonic spectrum, passive component sizes and motor drive efficiency. New generation wide band-gap GaN power semiconductor devices are utilized in modular topologies and they are compared with a conventional IGBT motor drive. The effect of phase-shifting between the PWM carrier signals of parallel connected modules and its contribution to size reduction is investigated. IMMD structure has proven to have a superior efficiency compared to conventional motor drives, thanks to the utilization of GaNs. It has been shown that over 98% motor drive efficiency can be achieved for 8kW IMMD by using a newly proposed topology where 2L-VSI converters are connected both in series and parallel on the DC link.