In Avowed's "Fires in the Mine" side quest, the decision to stop or support Darle impacts rewards significantly. While both choices offer XP, preventing Darle's mine explosion yields superior overall rewards.

Supporting Darle: This nets 1026 XP. However, it eliminates monetary rewards and further strains relations between Aedyrans and Thirdborn. Lying about your actions doesn't alter the outcome.
Stopping Darle: This proves the more rewarding option. You receive 1091 XP (212 for the kill + 879 post-debrief), 900 coins from Seynon and Kada, and loot from Darle's corpse: a Blackwood Branch (a superb upgrade material), Wild Mushroom Stew, and two Beetle Pies. The food is minor, but the Blackwood Branch and coin reward significantly outweigh the benefits of supporting Darle. Plus, it maintains positive relations between the Aedyrans and Thirdborn.
In conclusion, stopping and killing Darle offers superior XP, significant coin rewards, valuable loot, and a more positive narrative outcome, making it the optimal choice in "Fires in the Mine."