Definitely the Morag Tong.
Their Lore seems a lot more interesting than the Dark Brotherhoods, and I think the whole being sanctioned by the Temple thing is rather unique.
With that said, I do still prefer the Dark Brotherhood's questlines. To me they have a better "backstory" going for them compared to the Morag Tong's "Kill NPC X" quests.
Definitely the Morag Tong.
Their Lore seems a lot more interesting than the Dark Brotherhoods, and I think the whole being sanctioned by the Temple thing is rather unique.
With that said, I do still prefer the Dark Brotherhood's questlines. To me they have a better "backstory" going for them compared to the Morag Tong's "Kill NPC X" quests.