Hi,
OAuthToken == AccessToken
AccessToken == AccessTokenSecret
The name differences come from two different usages. OAuthToken and AccessToken come from the OAuth protocol names where, during authentication, Twitter gives you an oauth_token, that is exchanged for an access_token. As you probably already know, AccessToken and AccessTokenSecret are names that Twitter gives to the credentials on the application page, facilitating single user authorization.
BTW, LINQ to Twitter has a SingleUserAuthorizer.
Joe