The space in the car is how I choose, but I always have more than one format with me. If the wife and child are not going, all of my cameras go: 35mm-5x7. I throw the two tripods in the car and various sundries, a 12er of diet pepsi and have a hell of a good day. If the wife and child are going I tend to leave one or two cameras home, and one of the tripods. The LF stuff always goes. Diapers are added to the various sundries and less diet pepsi. My wife says I have a drinking problem. And still have a hell of a good day. What does not fit inside goes on the top. I hate choosing. I was only allowed to take one camera to Vancouver, the last time we went, and it was like choosing which child to leave behind.
I don't dare buy another camera, our couch was not meant to be slept on, and stray cats urinated in the dog house. The dogs won't even use it.