Sequelize JS - Which do I use? Model.key.references or 'Associations'?

I'm new to Sequelize. Current working on a small schema, needed to add a foreign key to a table, and found the following:

sequelize.define(
    "my_model", {
        "id": {
            type: Sequelize.UUID,
            primaryKey: true,
            defaultValue: Sequelize.UUIDV4
        },

        ...

        "linked_model": {
            type: Sequelize.UUID,

            // Should I be using this form to create foreign keys?
            references: {
                model: MyOtherModel,
                key: id
            }
        }
    }
)

A little later, I found out about the associations API - http://docs.sequelizejs.com/manual/tutorial/associations.html - Which can also be used to create foreign keys on related tables:

const Player = this.sequelize.define('player', {/* attributes */});
const Team  = this.sequelize.define('team', {/* attributes */});

Player.belongsTo(Team); // Will add a teamId attribute to Player to hold the primary key value for Team

The same question also appears here - Sequelize model references vs associations

Which of the two is considered best practice?