Not sure what everyone is arguing about here. Clearly SSD is better for intermittent r/w, whereas HDD can be more efficient at continuous r/w (especially in terms of watts/TB)
Just looking at specs should be enough to see that. SSDs can idle in ready state at close to 0 draw (~0.05w) whereas HDD requires continued rotation to remain ready. So consider an extreme case of writing for 1 minute then maintaining ready state for the rest of the day. For that the SSD will be far more efficient, obviously.