Inerters are specialized mechanical devices introduced into vehicle suspensions to provide an “inertial” control element, distinct from traditional springs and dampers. Formally conceptualized by Malcolm Smith (University of Cambridge), they are sometimes referred to as two-terminal mass elements. Although inerters have already been shown to enhance the dynamic performance of vehicle suspensions, existing research lacks a systematic comparison of their transmissibility functions under consistent excitation levels—and direct comparisons with both acceleration-driven damping (ADD) semiactive and passive suspensions. This work addresses that gap by performing mathematical modeling and estimating the transmissibility functions of body accelerations, wheel loads, and suspension travel for (1) a passive suspension in two variants—fully linear and nonlinear (the latter including internal friction and hysteresis effects); (2) a semiactive nonlinear suspension controlled via the Acceleration-Driven Damper (ADD) strategy; and (3) a passive nonlinear suspension augmented with a mechanical inerter. After determining these transmissibility functions, their dependence on each suspension configuration’s functional features is examined, identifying specific frequency ranges and parameter settings where performance can be most effectively tailored. Next, the influence of transmissibility on comfort, safety, and suspension travel is analyzed for selected, typical vehicle operating scenarios on roads classified according to ISO 8608. The results provide new insights into suspension system design and highlight the potential of inerters as an effective element in passive vibration control.