correction of statement

Most people would say, "I prefer coffee over tea."

You can also say, "I prefer coffee to tea."

The previous answers are correct. The issue is that "than" is used for comparisons of a particular quality or quantity. So you'd use "than" if you were to say "I like coffee more than I like tea" or "Coffee tastes better than tea." The former has you comparing how much you like each, and the latter compares their taste.

"Prefer" has that comparison built into it, so "than" is not necessary. You could swap out "prefer [it]" for "like [it] more than."

"I prefer coffee to tea."

Because I prefer sth to sth... or I prefer sth rathar than sth...

We spoke about the first.

I prefer beer to wine. I prefer you to him. etc