In Avowed's "Fires in the Mine" side quest, the decision to stop or support Darle significantly impacts rewards. While both choices offer XP, preventing Darle's plan yields superior overall rewards.
Supporting Darle: This nets 1026 XP. However, you forfeit any monetary reward and further strain relations between Aedyrans and Thirdborn. Lying about your actions doesn't alter the outcome.
Stopping Darle: This is the superior choice. You receive 1091 XP (212 for the kill + 879 for debriefing), 900 coins from Seynon and Kada, and loot from Darle's corpse: a Blackwood Branch (a valuable upgrade material), Wild Mushroom Stew, and two Beetle Pies. The additional XP, gold, and high-quality crafting material significantly outweigh the rewards for supporting Darle. Furthermore, maintaining positive relations between the Aedyrans and Thirdborn offers narrative benefits.
In conclusion, stopping and killing Darle provides the best combination of XP, gold, loot, and narrative advantages in Avowed's "Fires in the Mine" quest.