It's hard to say without knowing and understanding the precise physics and math of the situation that it could "just as easily" do one thing as the other. But I'm sure you're right that it doesn't *only* divert passing comets and asteroids. That it could have potentially helped steered some into Earth. My guess, though, is that many more were diverted away, as there are many more places where the Earth isn't than where it is at any given time, although Earth's own gravitational field would of course contribute to the impact probabilities.
...also, Jupiter would of course absorb many of the impacts itself, as opposed to steering them away or into the Earth.