Let me begin my answer by saying that the evidence is everywhere on this subject. It seems prudent to suggest that the choice of typeface has a relatively minor effect on the speed of reading or readability given our current understanding.
There is a section on the Wikipedia page for Serif that seems to directly address the question:
Serialized sources are widely used for body text because they are considered easier to read than printed sans-serif fonts. However, the scientific study on this topic has been ambiguous.
Here are some sources that seem to suggest that serif text has a statistically significant effect on readers (either through improvements in readability, recall or reader preference):
Certainly, the conventional wisdom (and what I was taught in the design school) is that the serif text tends to be easier to read. In general, the consensus of the research seems to indicate that there is no significant difference in readability or reading speed, only for serif reasons:
In fact, a greater difference in readability can easily be found within members of the same family type than between serif and sans serif typography.
It is important to keep in mind that academic research on readability is usually done by measuring reading time and / or comprehension; Factors that require long format text to be meaningful. In the use of short forms, such as signage, this is the best research I know about the readability of typography (and you can see that they are testing things like distance reading, word recognition and efficiency).
There is a great distinction between body copy (paragraphs of running text) and headings and other larger types. The Sans serif fonts (in their modern form, text without serifs has existed for thousands of years in prints and hundreds of years in handwriting (see street labels) were produced for larger and bolder uses, such as posters and The first commercially available sans serif font was designed for two large / very large uses.) It was not until 1832 (positively recent in the history of Western typography) that a commercially available minuscule sans serif face (to which it referred to then and now as a "Grotesque" type) became available.In those larger uses, there is no real suggestion, neither conventional nor other wisdom, that the serif text be better for that purpose (even in printed).
In general, "readability" is reduced to semiotics: the ability of the brain to convert curves and page spots into letters and words that have meaning. Hypothetically, the familiarity of a particular font should reduce the time (and effort) it takes to consume it (that's why the logos are so easy to process, you become so used to seeing those letters in that source in that order that you really do not need to read them to process the whole word or phrase having the meaning it has). In practice, the investigation. have He showed that familiar typefaces, to which readers have been exposed many times before, can be read more quickly:
The results indicate that the exposure has an immediate effect on reading speed
In a classic case of a chicken and egg problem, the fact that, in general, we have chosen serif fonts for long format text has meant that typographers have designed them in general for long format text. You rarely see a serif face with a height x as low as Futura or tiny counters as in some black faces and ultra bold without serifs, for example. They almost always have real italics (as opposed to obliques), include lowercase numbers much more often than without serifs and often have more flexible ligatures and other modern typographical features.
This does not mean that a typesetting book in Helvetica does not look beautiful compared to Garamond's similar type. There are abundant tricks in the designer's arsenal to match the playing field and improve the readability of sans serif (such as opening the first line and reducing the length of the line, as well as choosing fewer faceless geometric faces that include characteristics such as stress and distinctive forms).
In short: your choice of source is more important for brand and design reasons than for any other reason.