I don't know... Yeah, I liked the Oblivion Dark Brotherhood quests more, but I think it would have been cheap to essentially lift the same quests off the old game. For what it's worth, I think they're both of equal quality, just vastly different. I liked that each kill tended to have a unique item associated with it too. I have all the items (Aegisbane, Arentino Family Heirloom, Vitoria's Wedding band, etc) displayed on the mantle above my bed in Honeyside.
Why not they basically lifted off the Fighter's Guild quest from Oblivion into the Companions?
Two guilds Companion v.s. Silverhand
Fighters Guild v.s. Black Wood Company
Black Wood Company does something devious to FG member
Silverhand does something devious to Companion member
etc.