Documents typeset using LaTeX just look better than than their MS Word (or equivalent) counterparts. LaTeX has many well-known features to make document creation easy. However, it is some of its lesser-known features that together produce a professional-looking document.
Interword spacing is optimised
When using justified text, Word will (i) fit as many words on a line, (ii) add an even amount of space between these words, and (iii) start a new line and repeat. In contrast, LaTeX uses an algorithm to find the optimal spacing for the whole paragraph. This, along with its automated hyphenation means paragraphs are typeset with consistent spacing, not a combination of thin and thick spaces.
Superscripts and subscripts are the correct font weight
Subscript and superscript text are not simply scaled-down and vertically nudged text. To make these characters best fit with the rest of the text, they need to have the same weight. It’s best explained with examples:
The difference is subtle, but note how the subscript and superscript characters in the Word examples are slightly thinner than the other characters. This is not the case for LaTeX.
Appropriate margins are imposed
The default page margins in LaTeX are larger than you might expect. But there’s a reason for this: it keeps the number of characters per line to an optimal value. A reader will have the easiest time reading your work if there are 45–75, ideally around 66, characters (counting spaces) per line1. A typical document with one-inch margins (the default for Word and other programs) will have closer to 100 characters for 12pt font.
Admittedly, in many situations you will want to decrease LaTeX’s margins, which is easy with the geometry package. Nevertheless, it’s better that you are required to decrease them from a wide default value. Like many options in LaTeX, default values are based on good typographic practice and changing them requires a decision on your part as to what the new value should be.
Widows and orphans are penalised
A Widow is typographic jargon for a single line of text (or even just one word) by itself at the start of a new page or column. An orphan is a single word by itself at the bottom of a paragraph. Avoiding both of these makes the blocks of text on the page look much more consistent and professional. During compilation, LaTeX attempts to avoid producing widows and orphans provided that doing so doesn’t produce more severe typesetting problems.
References
Brushing Up Science 