Two different types of users, one model?

I have two types of users and am trying to determine the best way to model this.

The first type of user is the traditional kind. They sign in with Twitter and can comment on posts, etc. The first time they sign in with Twitter we ask for their email address and to confirm it so we can create the account. Let’s call it the Traditional User.

The second type of user I consider more lightweight. Basically they are just a subscriber to our newsletter so we really only need the email address (and for them to confirm it). Let’s call them a Subscriber User. Authentication isn’t frequently needed, but use single sign on tokens when necessary. (Not super secure, but good enough.)

A Traditional User might also be subscribed to the newsletter, and a Subscriber User might want to get a full account and become a Traditional User down the road.

Where it gets interesting is that the newsletter is personalised based on the categories the user subscribes too. These subscriptions also happen to play a role in functionality that’s strictly available to Traditional Users.

Now my question is what the best way would be to model this.

Would Single Table Inheritance be a good approach for this? Or would it be better to have a stripped down User class with everything Subscriber Users need, and then an optional Profile association for Traditional Users?

I’m using Devise with OmniAuth.