Hi Jream,
We went for a double cab because we want to take friends/children with us from time to time. When there is only the 2 of us, we have plenty of room for the dog, and if he doesn't come, then we'll just use the space for storage.
We are planning an 8 week trip in April/May next year up to the very north west of Australia (Broome/Kununurra/Lake Argyle), and 2 friends are flying in to meet us there. They only have 2 weeks holiday available. We'll pick them up from the airport and then keep on driving!
We also have grown up kids who will occasionally want to join us.
The 'visitors', whoever they may be, have to sleep outside in a tent, although I am looking at a tricky bed setup across the rear seats of the double cab...