What is the preferred method for specifying type families, after loading a font package?

Question

I'm confused about the methods used to specify fonts using when more than one package is potentially involved. I understand that packages configure a variety of settings by default, and that different packages support different options (giving different degrees of control over these settings), but is there a general rule or best practice?

For example, once I've loaded a package for the serif font, what is the difference between then using

\usepackage[scaled]{beramono}

and

\renewcommand{\ttdefault}{fvm}

to select the typewriter font?

The implication of some documentation I've read (e.g., mathdesign, 4.3) is that that packages may do some things to ensure that the "low level" way of specifying additional families will work smoothly with that package.

So, once I've loaded one package, is it better to specify subsequent fonts using the second approach above, or the first?

Answer 1

Always use a higher level method, when available.

The main difference here is that

\usepackage[scaled=...]{beramono}

allows to specify a scaling factor, while \renewcommand{\ttdefault}{fvm} doesn't.

In the case of beramono you need also

\usepackage[T1]{fontenc}

because the font is available only in T1 encoding.

Section 4.3 of the mathdesign manual refers to low level commands but it shouldn't be taken as an authoritative source. For instance, the official manual "Using common PostScript fonts with LaTeX" (texdoc psnfss) says differently.