Question: This is not a technical question. However as the FAQs say this place is about

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> people who love to create well-structured and beautifully typeset documents
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I take my shot.

I am often confused when which font family is more appropriate. Most people would suggest: "take what you like the most". But there are typographicaly reasons and I don't want to pick a font familty randomly.

I am looking for some good paper reasoning about the choice of font family, no luck so far. Are there good sources?

Answer: 
I know the question is about typography (i.e., aesthetics), but maybe an overview over several *scientific* studies which compare the legibility of typefaces is also interesting:

[Which Are More Legible: Serif or Sans Serif Typefaces?](http://alexpoole.info/blog/which-are-more-legible-serif-or-sans-serif-typefaces/)

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> Finally, we should accept that most reasonably designed typefaces in mainstream use will be equally legible, and that it makes much more sense to argue in favour of serif or sans serif typefaces on aesthetic grounds than on the question of legibility.
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Since aesthetics cannot be determined scientifically, the only important reason to prefer one typeface over another is really your personal opinion—but often it helps to stick to traditions.
Serifs are used for traditional things, and with themes like "corporate" and "formal", and for books & novels, etc. I use Sans Serif when the themes are "modern", "fun", "Colourful" and "playful"