This is a common misunderstanding for us foreigners, but manga and anime are not really comparable. Manga comes first, and only if the manga is good enough or has potential as an anime is it ever presented as an anime. Certainly people will have their preferences, as they always will, but they are simply two different ways to do the same thing, presenting a story to an audience. The differences that are most notable are simple restrictions on possibilities, of which there are many. In the same respect as Movies/Shows based on a book series, the content must be shortened or lengthened to the appropriate time constraints. That's not the fault of those producing it, that's simply how it must be done.

So do I prefer one over the other? Yes, I prefer anime because it can more easily represent the emotions of the characters, but I still like manga for the same reasons.