Over the years I've had quite a few cats and I have to say that the only time they've been in my car is when they've been on a trip to the vet for one reason or another. When it comes to dogs, I also see them as they rely on us a lot more than a cat does and they aren't as independent as cats, that's why I think they'd enjoy the car journey more. Taking a cat on a car journey for me would be as if you're taking the cats independence away from it and your effectively making it go where it might not want to. I can only imagine that as far as a cats concerned, being put in a box and then transported to a different part of the world, a part it's not familiar with would be the last thing it wants, and that's why when you open the cage door to let a dog out it bounds out, happy to be free, with a cat it's a lot more wary of everything that's around it and more often than not won't move for a number of hours unless you force it.
At the end of the day, I just don't think its natural to take a cat out of it's comfort zone more times than you should, and while taking it on car journeys might seem like a good idea to us humans so it can experience more parts of the world, I'm sure the cat would much rather we left them at home and for us to just take the much more inquisitive dog instead!
