Una sugerencia.

although similar to the previous one, it is better to use "in"

I think in the context of a walk, you would probably use either of these words, depending on whether you go up or down along the walk.

So you might use an expression like "total ascent" or "total descent", probably favouring the former, as this is the information most walkers want to know. It gives you an idea of how difficult it is. How far you go down isn't so important. See, for example, this page of Lake District walks:

http://www.lakedistrictwalks.com/ldwalks.html#north

Or this description of a hike in Yosemite:

http://www.tierrawiki.org/wiki/Image:Halfdome.gpx