Studies have already demonstrated the successful use of linear semiactive damping devices, such as variable orifice (VO) dampers, for semiactive TMD systems. More recently, nonlinear semiactive damping devices, such as magnetorheological (MR) dampers, have also been shown to be effective for semiactive control of TMDs. Though semiactive dampers differ widely, with responses ranging from linear (VO) to nonlinear (MR), criteria for choosing an optimal semiacive device for a TMD have not been rigorously developed. This paper expands knowledge of semiactive TMD systems by assessing the effect of nonlinearity in the damping device on the effectiveness of a semiactive TMD. This is achieved by simulating a variable damping device (linear), and a variable friction device (nonlinear). The variable damping device consists of a VO damper, while the variable friction device consists of a new mechanically robust and reliable damping device with a dynamic resembling the MR damper. These simulations allow the influence of nonlinearity to be investigated and provide further insight into selecting an optimal semiactive damping device for improving the performance of a passive TMD.