Well, I don't know first hand, so I have to quote the FAQ (only stuff that doesn't concern level and loot scaling):I'd be interested to know what the things are you dislike about Oscuro's? Besides the lvl scaling and the loot scaling, I often wonder what else is going on under the hood in Oscuro's mod.
FAQ said:"Oscuro's Oblivion Overhaul also adds many new things to the game world, ranging from new creatures and NPCs, to new sets of armors and even new text books. The addition of all of these actors and objects are carefully balanced against the original design of TES IV: Oblivion, as well as attempting to fit within the Lore of the TES series as much as possible. Many of these new additions are product of the modding community of texture and model artists, programmers and other miscellaneous roles. I am very grateful for their work and for featuring it within the world of Oscuro's Oblivion Overhaul.
Finally, this plug-in balances many smaller and less sweeping aspects of TES IV: Oblivion's gameplay. These changes affect things as diverse as combat AI, previously lackluster skills, character birthsigns, quest difficulty design, random bug fixes and enhanced functionality. As always, the detailed readme files inside the uploaded files contain very specific and extense information detailing the extent and nature of all changes."
OOO changes the whole game. You won't get some of the info in the FAQ, because it will be revealed in quests. Which means that it adds quests. As the name implies, it's a complete overhaul. I'd like it to be more transparent. But I heard that the newest version has some kind of installer that asks you questions, which would be an improvement.