Advantages and Disadvantages of using the same panel for admins and customers

I am creating a sort of CMS to manage gyms. I want to create a control panel for customers and for employees. I don't know if it's better to create two separate panels, something like:

http://ift.tt/2rN8RLX

and

http://ift.tt/2smMZnM

Or if I should create just one, something like:

http://ift.tt/1Kmzuog

And give more permissions to each type of user.

I know there are many ways to do this, for example Wordpress uses only one panel for all users and each user has different permissions. But is that the best way to do it? Or what are the advantages and disadvantages of each one?

I would like to say that in my implementation the employees and the customers are stored on the same table (but employees have higher permissions).