If you really care about Facebook likes, don't just post your stuff to Twitter and then rely on it being republished automatically to Facebook. In my sample size of one, Facebook penalizes you significantly for that and shows that content to far fewer people.
I have Twitter auto-post to my Facebook page, and I occasionally post things directly to Facebook as well. I've always noticed that the direct-to-Facebook approach generates far more likes, but I've never actually gone back and run the averages.