Anecdotally: at university I observed that my fellow students tended to prefer philosophy lecturers who told interesting little stories, jokes and asides. But whilst entertaining at the time, I always preferred the lecturers who just got down to the arguments etc., because they provided a constant stream of substantive points and arguments for me to write in my notes. And getting relevant material written down is actually useful for learning and getting good grades, whereas thinking 'what a caution that lecturer is', and expanding one's repertoire of philosophy jokes and anecdotes isn't.

On the other hand, I did have a couple of maths lecturers who managed to combine getting down to the nitty-gritty with some effective crowd-pleasing moments, which afforded one a break from concentrating for a moment.

So, for my part, I would tend to agree that if helping people learn is the goal, tangential 'interesting details' should be minimised.