Let's see... which do your prefer out of your main character in an RPG? Do you prefer him to never have any dialogue or do your prefer him to?
There are positives and negatives on both sides. If he never speaks, you get to fill in fill in the blanks yourself, which really enriches the role-playing experience. However it seems somehow more... empty, I guess would be the word for it? If your character does have dialogue it definitely stops the conversation from seeming to thinned out and one-sided, but on the other hand it's totally killing the role-playing aspect and it's really nothing more than a book on your TV screen where every once in a while you run around and achieve some goal to read the next set of text. That can pretty boring. (Xenosaga... zZzZzZ...)