As an atlatl expert (I watched several YouTube videos) they have an upward launch trajectory and seem to be ideal for longer-ranged flat ground engagement. This would suggest more utility for forest and open plains hunting where terrain advantage does not exist.
As I understand it, the atlatl enabled much more efficient and powerful throwing without much loss of accuracy. A brief search for figures says it can hit a grapefruit at 40m range
“For an experienced atlatl thrower, the mechanical advantage of the atlatl over throwing with the arm alone is about 6:1. Thus, if you can throw a dart 15 meters with your arm alone, you could throw it about 91 meters with the atlatl.”