Events drops higher or low level

Higher difficulty quests drop more materials. Check out the Currency drop rate sheet from this - https://docs.google.com/spreadsheets/d/1TaaCBOltXMMfh12knvJ0855oO_PMGzB19-U6xb2R0UI/edit#gid=30100714
Credit goes to Meliran.

As mentioned, the drop rates in higher difficulty quests is better. But drop rates aside, the increased exp that you get from the higher difficulty quests is also worth noting (depending on your current level, I suppose).

I was significantly underestimating the difference that the extra exp makes. I'm pretty weak, so I was just farming the Advanced (30 AP) difficulty. Then I accidentally clicked on the Expert difficulty, and was surprisingly able to do it. Just increasing the difficulty by one notch yielded three times as much exp. Then I decided to go ahead and try yet another level higher, and found out that I can actually do the Explosion difficulty on some of the nodes.

At that difficulty, I am getting a level every 2-3 runs, which refills my AP, so I can basically just farm non-stop. So even if the drop rates weren't higher, I would still run as high difficulty as possible. When I was doing Advanced, I wasn't really getting enough exp to level any time soon, so I could just do 2 runs and then wait like 6 hours for my AP to regenerate, then repeat. Going to the higher difficulty quests made such a huge difference for me.

TLDR: Do the highest difficulty quests that you can manage, imo.