Instead of electric dynamometers also hydrodynamic dynamometers can be used to load an internal combustion engine at a test bench. Hydrodynamic dynamometers combine high power ratings with low moment of inertia and offer especially in case of high power ratings a good alternative to electric dynamometers. Despite these advantages hydrodynamic dynamometers are not widely used in dynamic testing as modeling and control is due to their nonlinearities a nontrivial task. Using new concepts for torque control and speed control a significantly better performance with respect to the classical implementation is achieved thus opening a new path for the intended use of hydrodynamic dynamometers in dynamic testing. Hydrodynamic dynamometers are compared with electric dynamometers in reproducing operating conditions an internal combustion engine would undergo in a vehicle. Therefore, measurements have been performed at a heavy duty truck engine test bench with both type of dynamometers and different dynamometer controls. The dynamic capabilities as well as the effects of employing a purely passive dynamometer and different dynamometer controls are analyzed.