There's also a third viewpoint I'm aware of, which says that the second viewpoint is a myth that comes from the fact that serif fonts tend not to reduce well on pixel screens, making sans type the better (least worst) choice for long passages of on-screen text or poorly-printed reproductions, but serifs still the best for long passages of printed type. Within the last decade or so - certainly since reading on screens became commonplace - I've seen an increasingly common viewpoint that this is an outdated myth - that actually, serifs are faster for reading long text for no reason other than that we are historically accustomed to reading long passages of serif text, and that long passages of well typeset, well chosen sans can be just as good for readability and fast reading, as people become accustomed to it. Sans-serifs, according to traditional wisdom, are better for legibility - the letters are simpler, less room for error - and so are better suited for short text, like road signs. As I was taught, this is the reason why book typesetters almost always use moderately florid serifs like Garamond. The eye passes over the text more easily, there is less "fatigue" on the eye, and reading speed is improved. So, old-school wisdom (certainly, how I was taught back in the day) says that serif text improves the readability of long passages of text. Let's see if we can get a good, nuanced, ideally evidence-based answer. It's an old question, but an important one.