It depends. If you're driving through Nevada, then it's definitely the destination.
However, if you're driving through the Giant Redwoods or along the California coast, for sure it's the journey.
"Which matters more - the journey or the destination?"
All I can say is, I'm glad my wife and I took vacations in our 30s and 40s, even when it strained our budget, instead of waiting until we retired and were more financially secure. Our retirement mainly consisted of me caring for her as she faded away from a terminal illness.
We were in Brisbane Australia and our next stop was Sydney. We could have flown, but we chose to take a train. It was a very good choice, the folks on the train were friendly and we got to see the countryside. Flying would have been no different from flying over Florida. There were little towns with aboriginal names and you never saw so many sheep.