MongoDB schema design for multiple auth user accounts

I am about to build my node.js / express / mongoose / passport application and I am thinking about the right schema design for users and accounts.

There will be users loging in from twitter and facebook as well as from native accounts. At a later stage I want a user to connect both twitter and facebook with my application (and maybe even more external accounts).

I can not think of a good solution for that situation. Here are the options I am thinking of:

1.Having a profile model and account models. Profile documents represent the unique user, while an account provides either username and password (internal account) or the authentication data from the auth-provider (external account). A profile has to have at least one nested account document.

var ExtAccountSchema = new Schema({
    type: String, // eg. twitter, facebook, native
    uid: String
});

var IntAccountSchema = new Schema({
    username: String,
    password: String
});

var ProfileSchema = new Schema({
    firstname: String,
    lastname: String,
    email: String,
    accounts: [Account] // Pushing all the accounts in there
});

What I dislike about it are the not so consistent account documents resulting from different account data and the fact that I have a hard time finding the right account when my user logs in (searching uids and account types in nested documents -.-)

2.Having all data in a single model

var ProfileSchema = new Schema({
    firstname: String,
    lastname: String,
    email: String,        
    twitter-uid: String,
    facebook-uid: String
    password: String
});

Well this is just ugly -.- It might be easier/faster to find the right account data but it's not nice to maintain.

Is there a better solution? Is there a best practice?