They're both very expressive. Opera used to be in common languages instead of "foreign" languages like Italian or German, so people could actually understand the words. Nowadays, each time I've been to the opera it has had supertitles. It's not difficult to know what is going on if you don't read the programme.

Ballet is a bit more like miming, but overall, the plots are still obvious, and frankly, very thin. We don't watch the Romeo and Juliet ballet wondering if they will survive or not, but rather wondering how they will express their anguish and suffering through dance.