Should you go after Aether, Poseidon, or Demeter first in Horizon Forbidden West?

gamepur.com:

After meeting GAIA face to face in Horizon Forbidden West, Aloy is given a choice. You can go after any of the three subordinate AIs in the world, Aether, Poseidon, or Demeter, but the decision feels crippling like you’re missing out on something if you take the easy path. This guide explains what each choice means, so you don’t feel like you’ve headed out in the wrong direction.

GAIA presents this choice to you with a level requirement for each AI. Aether is a level 17 quest, Poseidon is a level 22 quest, and Demeter is a level 24 quest. Each one is in a different location, and some, such as Poseidon, sound more interesting than others. While we recommend that you stick with the quest that’s appropriate for your level, that factor may change soon after making this decision.

The only difference between choosing one AI over the other is the dialogue that GAIA speaks. She’ll discuss that particular AI but mention that Aloy can decide to pursue another one at any time. Then, you’re given a choice to head west in pursuit of your first AI or go back east to finish up any side quests that you’ve missed. Of course, this means that your level could be much higher when you return.

Finally, when you leave to go west, you’ll be given three new main quests. You can pick any of these, so the decision you made with GAIA has no impact at all. However, you can only carry one AI at a time, so once you’ve picked up an AI, you’ll need to return it to GAIA before you can go after another one.