I've never been on an RS tour, so I don't know if some customers prefer to have most of their visits arranged for them and guided, as opposed to Independent Travel. Auschwitz is also a big time commitment.
I don't know if you want to "calculate" the "value" of one visit over another. I mean, we skipped the salt mine, because we don't care. We felt we were lucky to get a last-minute ticket to a concert in an important Synagogue, because the extra concert lighting made it much easier to see the architecture, and we weren't bound by the open-hours of the place. I suppose that The Schindler Factory is a must-see (because everyone will ask you about it.). But it doesn't give you a touching insight to "Schindler's List" (the movie) because it's not about the movie. It's really an "Occupation of Krakow" museum, with 10% dedicated to Schindler and his secret project. It's just as crowded as Auschwitz, but not exposed to heat or cold like outdoors. I found it claustrophobic. I would say that the Resistance museums in Amsterdam and Besançon (France) did a better job of trying to show you what the locals, other than Jews, faced. The rigid fixed-time tickets at the Schindler Factory are a problem, like the Auschwitz tickets.
We've been to Buchenwald as well as Auschwitz, and indeed it's a big factor that so much of Auschwitz is still intact. The vast crowds, and the dedication of individual barracks buildings to specific victim groups (so that they are not really "public", I simply mean ... ) take away from the experience. But I think it's an essential visit.