Is there a reason why I should not make use of commands such as \bf to bold my text instead of the "standard" ones?

Question

The question arose eversince I learnt about \textbf{} and I couldn't quite spot any differences against \bf.

Answer 1

\bf has not been defined by default since LaTeX2e was introduced in 1993. Some classes may define it for compatibility with old documents but that can not be assumed.

\documentclass{minimal}

\begin{document}

this \textbf{that}

\end{document}

But

\documentclass{minimal}

\begin{document}

this {\bf that}

\end{document}

produces the error

! Undefined control sequence.
l.5 this {\bf
              that}
? 

Even when it is defined, the behaviour is not the same as \textbf as it ignores the current font settings:

Note that that is not italic here, but \textbf gives bold italic in an italic context.

\documentclass{article}

\begin{document}

\itshape


this {\bf that} \textbf{the other}

\end{document}