On the net, many treatises talk about the .otf format as "stronger" or "more stable" than the .ttf, and the fact that the .otf have features that the .ttf do not have, like ligatures, small caps, alternates etc.
See for example this page (I don't know how old):
Yet many .ttfs allow me to use those features not only with LaTeX, but also on LibrOffice. Now what is the current situation? I don't want to open the usual inconclusive flame, but are there reasons to prefer .otf to .ttf?