I think I like the combination of all of them. Slim Shady is fun but It’s not something I would like to deal with non-stop. It's a shield. Eminem is cool but a little bit from an unreal world if you know what I mean. It’s part of the image, like a package. You see the cool and shiny surface but you don’t know what is hidden inside. I think Marshall is the chocolate inside of Eminem candy.
he's a complicated person which all kind of flavors. He can be sweet, sour, plain...
Marshal/Eminem/Slim Shady is a very interesting and complicated person. All of his personality features are important and bring both positivity and negativity IMO. He wouldn’t be the same and complete person if one of them was missing.
If I have to chose only one of them, I think it would be Marshall. I have no idea what kind of person is hidden behind Eminem since I don't know Marshall Mathers. I can only assume from various signals and impressions he made over the years. For some reason, I think Marshall the core. The most important part of him.