Not very helpful, I must admit. But there is a good reason. Let me explain by way of some analogies.
About the time that researchers were asking about the differences between serif and sans serif, other researchers were asking whether white people were more intelligent than black. Typography is not quite as controversial as race (unless you’re a professional typographer) but one of the questions one asks as a professional researcher in any area is why is a particular difference worth measuring—whether it’s the difference between serif and sans serif fonts or white and black people.
If you mix with lots of fonts, just as when you mix with lots of people of different colour, you discover many subtleties of quality. All serifs are not the same, just as all whites are not the same, and—shock horror—some fonts, like some people, are not purely one or the other. There are mongrel fonts in our midst that might be better on some occasions than the pure bred!
The point is that life is subtle and asking the question whether we should use serifs or sans serifs is as crude as asking whether or not we should employ only whites or blacks. The question tells us more about the person asking it than it does about the question topic.
At one of Europe’s leading design schools, students doing their undergraduate degree were allowed to use only one family of fonts for everything: Univers. This may seem a bit extreme, but it did mean that students got to know well at least one major font family. Later, if they worked with other fonts, they were likely to realise that they needed to get to know a new family in some depth before they were able to use it appropriately.
But there are other reasons why the question of serif vs sans serif is not a good one.
Douglas Adams’s Hitchhikers’ Guide to the Galaxy has a lovely exchange between a marketing person and Arthur Dent (one of the main characters), set in a Stone Age Earth: Arthur has been sneering at the marketer, saying that she and her companions (telephone sanitizers and hairdressers) have spent six months in committee, and they haven’t so far managed to invent the simplest of technologies, the wheel. Holding up a hexagonal, varicoloured object, she turns on Arthur and says: “Ok wise guy, you tell us what colour it should be!”
Well, people who ask me about which fonts to use are a bit like the marketing person. This is a choice one makes AFTER one has made some rather more important decisions like:
• what do you want people to do with the document?
• what different types of task are they going to want to undertake?
and so on…
And going back to my first analogy: it’s a good idea to develop a precise job description for an employee and then recruit someone who can do the job, rather than start the job description by saying only serifs need apply.