Short answer: It’s going to vary by student.
Which, admittedly, isn’t a very satisfying answer.
But it’s especially hard when one’s pushing against surrounding culture. To take your specific example, @homerdog, you said that no high-stats students from your kid’s school go to safeties. That’s a heck of a weight to push against, you know? On the other hand, kids at my D17/D19’s high school only very rarely go to hyperselectives—last year they had a graduate go to Wellesley, but that was a bizarre outlier that people are still talking about. (My D17 went to the most selective from her graduating class, a LAC that’s often described on CC as a low match or even a nearly-safety, not a reach, for non-tippy-top high-stats types.) Because part of what defines adolescence is the need to fit in—so adolescents (well, and let’s admit it, us adults too, it’s just not usually as intense) are constantly working to define themselves in relation to their peers’ norms.
I think one thing that helps, though, is figuring out what moves a student. So my D19 has one astonishingly easy to get into school on her list—seriously, the 25–75% ACT range is **19/b to 25—her deep safety, that remains on her list because she’s absolutely in love with the way they’ve crafted their gen-ed curriculum. Yeah, it’s inside baseball and nerdy in an odd way, but it’s what’s important to her, and so if she ends up going there, she’s got a hook that makes it all the easier to see the other good things about the place.
It’s also important to know a kid’s turnoffs. My D17 was very interested in Alabama—until she saw in person the centrality of sorority life, which was a big no to her (in the same way it’s a big yes to others). And I’m still convinced that she would have thrived there—but that was a big negative to her, and it made it really, really hard for her to see all the positives (that, to my mind, would have outweighed the negative). Okay, fine, so that’s a safety she wasn’t happy with. So knock that one off the list and move to the next idea, you know?
So I really think it’s the hook. We talk about that on the part of the applicant, but I think it’s important for the school. For my D17, the hooks are things like gen-ed curricula, compactness of the campus, and what I can best describe as a “relaxed” vibe. For other students it’s Greek life, or the football team, or the lab facilities, or even—and yes, this is a hook in this sense—perceived prestige. And like I said from my D17’s example, once a hook has clicked, it makes it easier to see what else is good about the school. And any given student (important caveat: any given student who’s engaged in the process) will have multiple hooks that would work for them, I suspect.
Anyway—I got longwinded, but hopefully it makes sense. And, of course, as with any advice on this sort of forum, you individual mileage may vary. But I think this at least gets close to the reality.