That is a question that cannot be answered in a "black or white" manner. The decision whom to play at SF is and will be a decisive moment for close games, and I´ve won (and lost) games due to missmatches at this position.
I prefer a game-by-game decision about the use of the teams ressources - I´m not the kind of coach to run a S5 and wait for good things to come but to alter lineups in combination with tactics in different ways and using players - if they somehow fit the needs - on different positions over the course of a season.
While this might fail badly on NT teams, where the players are heavily specialized, the raw material of U21 players and the "holes" in opponents lineups might open up ways of using even a limited amount of overall skill to create missmatches and surprises.
So going back to your question:
I love guards who are able to pass and PFs who are able to defend aswell as PG types with high Driving / Inside Shot at SF. Which of those three types will be used is based on tactics, opponent, player material available and a "mad scientist" influence.
Zwei Dinge sind unendlich, die Dummheit und das All...