Drops give your back a rest as sitting upright has all the weight on you back and legs.

Once you feel comfortable in the drops you can use that position to stretch, and to give your body some variation in movement.

I also find the drops helpful when going around corners as well as picking up speed on the flats. With practice you can learn to go downhill and around corners with ease and control. After awhile you will love downhill- a nice reward for all the work it took to get up the other side! It all takes practice, practice, and more practice just like everything else in cycling!