Critical comparison is presented related to the stability behaviour of milling processes performed by conventional, variable helix and serrated milling tools. The paper presents a general milling model linked to any non-proportionally damped dynamic system. Extended multi frequency solution and semidiscretization are implemented and used to calculate the stability of stationary milling. Measurements performed in industrial environment validate the general numerical algorithm that is able to predict the stability conditions of milling processes carried out by cylindrical cutters of optional geometry. Both the calculations and the measurements confirm that, for roughing operations, the highest stability gain can be achieved by serrated cutters. It is also demonstrated that variable helix milling tools can achieve better stability behaviour only if their geometry is optimized for the given cutting operation.