Mechanical and thermal irreversibilities, with regard to a decrease of technical and economic efficiency, have different influence on different types of real power and cooling cycles. In the following paper, for comparison two thermodynamic evaluation numbers, named the mechanical strain ratio and the thermal strain ratio, are defined. They are used for investigation, to which extend reversible thermo-dynamic cycles, with regard to transition to the respective attached irreversible cycles, are sensitive to irreversibilities. The results of this investigation are discussed. This confirms the usefulness of the newly defined two thermodynamic evaluation numbers.