Pretty much just as unsuited. Even if a van has 3 times the area available to solar panels it's still a negligible amount of energy...
By the way, the best book and/or course I've read for building intuition for these kinds of questions is "Physics for Future Presidents" by Richard Muller. He used to teach it as a course at CMU and I believe the lecture series is still available to watch or listen to online. Very worthwhile.