I looked but couldn't find any other post commenting on this, so I tried an experiment.

<span class='standouttext'>Spoiler : </span><span class='spoiler'> </span>










When the creatures asked me to help them kill the demon for them, I responded, "Not interested" & received 51425 xp (not sure what the bonus is here without wisdom). Then I went in & killed the demon. When I came out & talked to one of the creatures, I received it says 32736 (35354 with wisdom bonus)& shadow leggings. If I agree & kill the demon I only receive the 32736 & shadow leggings. It makes me think that I shouldn't agree with other quests & then go ahead & do the quest to see if it makes it difference with those as well. Are there any others out there like this?