This paper investigates the impact of switching frequency and modulation technique on the efficiency of electric drivetrains utilizing inverter-driven Permanent Magnet Synchronous Machines, focusing on heavy-vehicle applications. Accounting for inverter conduction and switching losses, along with machine copper, iron, and magnet losses, a comparison between two- and three-level inverters is performed at key operating points relevant to long-haul truck applications. This study employs current-based finite element analysis for machine loss estimation and a virtual prototyping method for inverter loss estimation to analyze drivetrain efficiency. The findings indicate that there is an optimal switching frequency evidently improving overall efficiency. Moreover, the system using the three-level inverter demonstrates notably lower system losses.