Me. I've got an extensive dental history. Unfortunately genetics has handed me very weak teeth. Anyway it sounds like yours is just preventative if you haven't had any damage to the nerve tissue. In other words, if you don't have a toothache from it, then try the filling if you want. If you do, then I'd get the root canal.
It isn't all that painful like people try to say. If I could afford it I'd get a root canal on every tooth. What they do is remove the nerve tissue from the tooth, along with everything elso from the inside, and fill it. You don't need this nerve tissue once your teeth have grown in. It just allows your teeth to feel hot and cold. A real pain if you've got sensitive teeth.