Even the same hill can be measured in two different ways. Here's the elevation profile of a local 'hill' if you were to ride it in the north-south direction:
It would be a completely different hill if you were to reverse the route and go south-north! This hill is 2 different climbs.
#1 most obvious statement, is that if you go north-south (left to right on the elevation profile), you are starting at a much lower elevation and have way more vertical gain!
#2 is that for the north-south direction even if you were to start at the same elevation (1215ft), the grade is much steeper - the south-north direction (right to left) is longer but gentler
#3 is that the south-north direction is not only gentler, but includes a bit of flat and even slight downhill, which gives you a chance to rest