In the case of (La)TeX I'd actually also be curious if i.e. the rules governing hyphenation/justification makes any difference as well, not just the typeface.
I'm pretty sure they do. Justified text looks more "professional" than ragged right one. The problem with it is, that it can create rivers without proper hyphenation. TeX is pretty good at this stuff and that's one reason why text set with TeX looks so good. I wish browsers would catch up on this.