Cfrgtkky

Is either of these considered better/more readable/more "proper"/more conventional than the other for making text bold? If so, what is the reason?

I like my text textbf{bold}

versus:

I like my text {bf bold}

Marc van Dongen gave a great answer. I'll throw in another reason:

it and bf do not play well together. That is, they do not nest as one would intuitively expect:

Whereas textit and textbf do play well together:

This is nice. However, you may notice that it still fails to handle nested style adjustments to small caps, since the Computer Modern fonts do not contain slanted or bold small caps:

If this is a problem for you, then use the slantsc package in combination with the lmodern package. slantsc provides, among other things, rmfamily (roman), ttfamily (typewriter/​teletype), sffamily (sans-serif), bfseries (boldface), itshape (italics), slshape (slant/​oblique), and scshape (small caps). With these, small caps can obtained in slanted form:

As a bonus, slantsc fixes textsl to behave properly with textsc, so you can continue using those if you like.

Alas, I haven't yet found a package which fixes the behavior of nested instances of textit. In typesetting, when you nest italics, you're supposed to come back out of italics to roman. For example, the word "Titanic" below is in nested italics (which should ideally render as roman, not italics):

Tanaka, Shelly. On Board the Titanic: What It Was Like When the Great Liner
Sank. New York, NY: Hyperion/​Madison Press, 1998.

As a workaround, one can usually write textrm to temporarily return to non-italics in those cases, but of course this is only valid if you know the exact number of nested italic levels, which may not always be the case, especially inside a macro.

Update:

As others have pointed out, textit and textsl do automatic italic correction, whereas it, itshape, sl, and slshape do not. Thus, you can write textit{stuff}, but you must write {it stuff/} or {itshape stuff/} to get the same effect.

In general the command (textbf/textit) approach is more useful if the text is followed by more text on the same line and isn't followed by a small punctuation symbol. If the text is in a paragraph on its own or is followed by a small punctuation symbol, it doesn't matter really. In that case the declarations (bf/bfseries and it/itshape) are equivalent to the commands. As pointed out be others, the declarations bf and it are deprecated and should be avoided.

To see why the commands should be preferred, notice that textit inserts an italic correction at the end, which adds a small horizontal compensation if the text ends in letters with long ascenders that would otherwise run into the next character. The declarations (it and itshape) don't insert an italic correction.

The fourth, fifth, and sixth row in the following shows why the commands may differ from the declarations. In the fourth row you get a proper italic correction, in the fifth and the sixth you don't and this results in the ff ligature running in to the h.

documentclass{article}



usepackage{booktabs}



begin{document}

  Huge

  begin{tabular}{lll}

    toprule

    verb|textbf{fluff} hair|    & textbf{fluff} hair

  \verb|{bf fluff} hair|       & {bf fluff} hair

  \verb|{bfseries fluff} hair| & {bfseries fluff} hair

  \midrule

    verb|textit{fluff} hair|    & textit{fluff} hair

  \verb|{itshape fluff} hair|  & {itshape fluff} hair

  \verb|{it fluff} hair|       & {it fluff} hair

  \bottomrule

  end{tabular}

end{document}

First of all you should not use the obsolete bf or it macros from LaTeX2.0. They do not use the new font selection scheme (NFSS) of LaTeX2e. So bf will do bold and bold only, but will not mix with an italic setting, which makes bold-italic impossible. Use the new bfseries macro instead.

There is not much practical difference between textbf{<content>} and {bfseries <content>}. I would say most people use (for short texts) the first usage because it follows the common somemacro{<content>} LaTeX style. The latter should be used if you want to make the rest of an environment/group bold, of course.

You should note that textbf uses bfseries internal, so the latter is a more fundamental macro.
The definition of textbf is:

ifmmode

  nfss@text {bfseries #1}%

else

  hmode@bgroup

  text@command {#1}%

  bfseries check@icl #1check@icr

  expandafter

  egroup

fi

So textbf switches to text mode inside math mode, while bfseries apparently doesn't.
It also adds checks for italic correction before and after the content, which is a great feature of LaTeX2e.

One benefit of bfseries is that it doesn't read the content as an argument, which would interfere with catcode changes required by verbatim content and other special code.

In summary I recommend textbf for smaller texts, mainly because of the italic correction, and in math mode. bfseries is IMHO more intended for environments and larger texts. One notable exception is if you have bold and italic (etc.) combinations, then you could write textit{bfseries <content>}, to avoid two sets of braces, but this is more a fashion choice. You should not use bf in modern LaTeX documents.