Yep, that's almost exactly how I see it too from a stylistic and tactical point of view.
Otamendi appears to have a slight edge in terms of being a more gritty and committed 'stopper' type defender who plays within his means instead of venturing forward and risking positional lapses, so functionally he suits more pragmatic managers that like throw-back, steady defenders in a slightly rigid and deeper defensive line to match their counter-attacking offensive tactics. Which is what Benitez historically prioritized like you rightly pointed. Or even the likes of Simeone, Jose (pre-Madrid and now at Chelsea evidently), and other archetypically defensive coaches for that matter.
Ramos is more of a Dutch school, Guardiola, Van Gaal type of centerback who in terms of his defensive commitment has a propensity to be more of a gambler for lack of a better term (has shown steady improvement to be fair), but is really balanced and confident in both aspects of the game and naturally fits into teams that prioritize high levels of ball possession and a higher defensive line - bringing his superior ball skills, distribution abilities, recoverability, greater attacking flair, and athleticism to the fore.
In that sense, Ramos is an almost seamless fit for Van Gaal and United. As for Benitez at Madrid I honestly dunno. Over the course of his career, he has shown a distinct lack of ability to be more flexible in his defense-oriented methods. Will that change somewhat under Perez' strict directive ? That much remains to be seen I guess. Although, wrt Ramos, he has come up leaps as bounds as a defender and a leader, particularly under Mourinho who really improved his positional discipline. So him thriving under Benitez isn't out of question from a more casual Madrid matcher's perspective.