Depends on the car. B bodies tend to weigh several hundred pounds more than A bodies so the extra weight in front is less problematic. If the big block theoretically makes more torque, it's needed to get the heavier car moving more efficiently. Though I've never driven one myself, big block A bodies are notoriously poor handling cars due to the unfavorable front-to-rear weight balance. HP being around the same or "close enough" between both engines, I'm taking the small block every time because of the weight.