^There are many variables that can contribute to a valley. Friction, temperature, winds, train weight, proper lubrication, ect.
To get it back, they will just pulll the train up to a high point and let it coast as far as it can.
I don't think it really looks better or worse. All three do what they can in the space/height provided. I think they are all really good looking!
This one just has more room to toy with, is all. I do like that it lacks a tophat, though. Thos are my favorites.