I go for wool blankets over fleece blankets because my understanding is that they are more fire retardant and retain more of their warmth value when wet... BUT... Fleece is lighter, more compact, and it dries faster... I often waffle. Inside the car, except for condensation or a broken window, it probably doesn't matter. But.... if we decide, for some reason, to hoof it, wool seems like a better choice for my for O/A, where it can be cold and wet.