custom user login/register menu tabs
It sounds like you're wanting the use case covered by the Profile2 Registration Path module: 


  By default, the Profile 2 module permits you to add fields from chosen
  profile types to the default user registration form. Unfortunately,
  there is only one user registration form. Thus, every user will be
  presented with these fields during registration. If you have two
  profile types targeted at two different audiences, you cannot have two
  separate registration forms.


Anything else, might need to be covered by a form/menu altering custom module or Tab Tamer.