I think either choice (driving or flying w/ lap baby) would be perfectly safe, statistically speaking, but I think flying with a lap baby would absolutely be safer, no question.
Car crashes are the #1 killer of kids, but even still the chance of having your child die in a car crash is incredibly small.
I personally HATE flying, so I'm not sure what I would choose. But if statistical safety is your #1 concern, I definitely think flying is the way to go.
I have to roll things around in my head for awhile....