I hate having to choose which car to take on road trips! It used to be easy because I had a baby truck with no AC so we always took DH's car. Now I have a nice new car, but we can't figure which car to take. It's a 5-6 hour car ride each way.

Take mine and put miles on the new car but be cozy and have lots of trunk space/back seat space (might have to tote around 2 other people once we get there).

Or, take DH's older car, has 5-6 mpg better, but smaller trunk (doable, just cramped), and is a 2-door car so we'd either have to cram the other two in the back, or deal with putting our car seat in their car. ETA: It's a very roomy backseat! Bigger than most 4-door newer cars

How do you choose?