Main reasons are the better and darker storylines. AOS isn't forced to add silly humor that kills the dramatic tension. Disney is trying reach the widest audience possible so that forces them to cater to the masses. AOS has more freedom to have darker and more adult oriented storylines. When I read comic books as a kid they had a serious tone about them that MCU doesn't have. MCU feels more like a Sat day morning cartoon than a comic book. AOS delivers that comic book feel that the MCU lacks. Not to mention the acting on AOS especially this season blows away anything in the MCU. When you have a great actor like Benedict Cumberbatch and force him to act silly with some cringeworthy humor thats uncalled for. They should take some lessons from the X-Men universe and allow the actors to act. Nobody in the MCU comes close to the performances of Fasbender or Mcavoy.