They both confess that God exists in three Persons but one being.
The difference is in the introduction of filioque in the Latin confession of the Nicene Creed. Although filioque was inserted in order to assert consubstantiality of the Father and the Son against Arian heresy, it is also a deviation from the Ecumenical Confession.
From Spain, ‘filioque’ spread to the Franks (present-day France). It was embraced by Charlemagne who went so far as to accuse the East of having deliberately omitted it from the ancient Creed. Pope Leo III (795-816) intervened, and forbade any interpolations or alterations in the Nicene Creed. He ordered the Creed, without filioque, to be engraved in Latin and Greek on two silver plates on the wall of St. Peter’s in Rome. Nevertheless, the addition was maintained by the Franks. History of Filioque, http://aggreen.net/filioque/filioque.html