I see a lot of conflicting advice about loglines, and I took a class that advocated that loglines shouldn't tease but instead reveal the central conflict. In the case of the Santa logline, I don't think it passes the test: we have the set-up, but it's not clear what the story/conflict will actually be about or even what genre it is. I like the Save-The-Cat logline formula to some extent, but, while it reveals the plot, it hardly results in concise loglines. I guess I remain confused as to which advice to follow.

I hear you, bookworm676. I have a Craft class called Story Summaries which covers everything from loglines to treatments to beat sheets, six different narrative summation types in all. And every time I teach it, loglines seems to be the thing that has left participants most baffled. So many theories and most I find that lead to more and more complicated summations which cuts against the whole "concise, concise, concise" mantra. Tell you what. I'll do a follow-up post with some key excerpts from my lecture on loglines. I offer two approaches. Let's see if that's helpful to you.