I believe it depends on the patient. Trauma's definitive care is surgery. Having an unstable medical patient is best treated on the scene. The longer it takes to get good care the harder it is to get them back or stablized. I mean if you think about it brain death occurs in 4 to 6 minutes. It takes longer than that to get loaded up and back to the truck. Then it's too late.
Treat them in your truck... take them out of their environment and put them in your controlled world. if its a code fight it out in the house for a little bit but once help is there.. get moved to the truck.