We have about a 14 hour window, if it is within 14 hours we drive more than that we fly. I HATE to fly with my kids. At least in the car we have some control over things, we eat when we want, stop when we want, if the kids cry it doesn't bother anyone.
We drove (from Northern AL) last year, 3 adults and one child cost $175 round trip so it is an enormous savings for us.
The other advantage for us is we get to take all of our stuff which I really like.