I recomend using the two of them to expand to every corner, however i think neither of them are "better" because they are slightly different, twitter is short and to the point, this can be a downfall with the 140 char limit, but users dont have to read through a novel to find a link attatched, on the other hand facebook is much more detailed and offers many other features, like picture albums. At the end of the day it is up to what you prefer and which one you are currently getting the most attention from. They both have an astonishing amount of potential.
Just use both. They are tools nothing else. FB is more about engagement and Twitter is more about sharing information very quickly across numerous platforms.
I think if it is for marketing then facebook is best because the more people know then more popularity because here we can find many users than twitter so faceboook is the good one for marketing.
My vote is on Facebook. I own a large social media advertising agency in Indianapolis, Indiana and we have seen a large spike in demand for facebook services.