Thanks guys.
We might be in a unique situation when it comes to inside space. We're planning on spending six months on the road this winter (from Oct - March) so inside space is maybe more important than the average 1 to 2 week holiday in the summer. We'll be spending most our our time in Southern California and Arizona so daytime temperatures should be ok, but night time and poor weather days may require staying indoors. When that happens its nice to have some comfortable indoor space to kick back in.
This may require making some hard decisions on our part. Do we go smaller on the trailer so we can purchase a vehicle we might use after returning home, or purchase a larger truck and sell it and the trailer when we get home. Either way we'll be selling the trailer, this is a one time trip. We don't usually camp in the summer, its just a method for us to escape Canadian winter for a year.
I really wanted to avoid going to a 3/4 ton truck but even using a Tundra (one of the few full size trucks I'd consider keeping) won't safely tow a 27 to 28 ft. (the box) / 31 to 32 ft. (with hitch) trailer.