in a fist fight id go winston, hes probably the toughest. as for the best at catching ghosts id say ray, hes an intellectual like egon, but alot better at translating that into hands on situations.
peter has the coolest head, so in an apocalyptic type situation hed be the best guy to have around, after ray "went bye bye" and egon was "scared beyond the capability of rational thought" peter and winston were left, but peters intelligence makes him the more useful. and egon would obviously be the best one at solving a complex problem, or at inventing something new to overcome it.
so in four different situations, id make four different choices, each one brings something to the team that the others dont have.