Choosing the correct Relative Value metric

Hi all, Can someone please explain to me the logic behind determining which market multiple is appropriate for valuing a firm when there is varying leverage? For example, for P/S ratios the kaplan books state that they do not capture differences in cost structures across companies. This I can understand because sales is at the top of the P&L statement. However for EV/EBITDA ratios it says that these are useful for comparing firms with different degrees to leverage - however EBITDA shouldn’t capture this effect either for the same logic as above. If someone could explain the rationale behind this that would be superb. Thanks!