Difficult TrekOn difficult treks, the chances of altitude sickness are high. The weather is constantly changing. Difficult treks are also classified based on exit options: There are a few or zero exit options; this means once you are in, you are bound to complete the trek.
The northern sections of the trail are more difficult and strenuous. The southern end (Coinciding with the Appalachian Trail) is more crowded. The northern sections tend to be more rewarding. There's something odd about beginning a journey at “Journey's End” (The Northern Terminus).