If someone were to go through the same area multiple times (if they died and reloaded, or with different characters), or did half of a larger area and let loose scorpions to wander around and finish off the rest, a difference in dropped loot may become apparent.
For example, a couple people suspected character level (or something similar) influenced the quality of items after they went directly for various unique equipment (ie dragon armour) as soon as possible, and found that they consistently got worse stats than they had in a previous game, where they had explored more and done more quests before getting the equipment. Ariana confirmed this in a game trying for the lowest possible character level finish (she hit the gong at level 12, to end up in the wastelands at level 17, then quit). Around character level 5 or 6 she reloaded a lot trying to get a holy sword with frost on it, but couldn't (and didn't get anything worth keeping). Trying again about level 10, she found it much easier to get good stats on the sword.
Since nobody using scorpions (or other traps / summons) has reported a difference, there can not be a dramatic change in loot between direct and indirect kills. Since nothing in the game mentions a penalty for using traps or summons, and it would not make sense to go to all the work of adding a penalty but making it too small to be noticeable, I would guess that there is no difference in dropped loot depending on how a creature is killed.