I've pointed out in previous blog posts that I'm not a fan of ORMs. What I'm even less of a fan of is code-first design, particularly in combination with an ORM like the Entity Framework.
It might seem cool and shiny and if you are just whipping up a small proof of concept or test app, please feel free to do it, but the minute you think of doing it for enterprise systems, just don't. And if you have colleagues wanting to do this, please just say no.
For most organizations, the data that they own is one of the most (if not the most) valuable asset the company has. The data will generally outlive generations of applications and just be morphed from shape to shape over time.
The data will often be accessed by many different applications, often created with different technology stacks. You might think you'll be able to corral all access to the data via your app; and again you'll be wrong.
So designing the data storage to suit the needs of a single version of a single application at a single point in time, is what we baseball umpires know as "a big call".
Umpires know to make calls like this emphatically and confidently.
But this is not a call that you should be making. It's the quickest way to start building disconnected silos of information that don't represent the business or how the information in the business is inter-related.