lower horsepower but higher torque figures of a diesel mean they have a narrow band ( think rev range) where that torque is usable, but it is really usable like you state for overtaking, mid-range pull etc. the petrol with its higher horses but lower torque is spread out more over the rev range, meaning the torque is a lot more levelled out, less oomph or push you into your seat, but its higher horses mean a higher top-end speed.