The scriptural stance is that neither do.
No one who denies the Son has the Father. Whoever confesses the Son has the Father also. [1 John 2:23]
Rejection of the Son is rejection of the Trinity in toto, therefore they are rejecting God. Worshiping a Unitarian God rather than a Trinitarian God is worshiping a different God, because you are denying the makeup of His very Being, and the way the Trinitarian persons interact.
Christ was a fulfillment of the Law and the Prophets, not Judaism (Mt 5:17; Lk 24:44). The Judaism of today is not the Judaism of Jesus’s time, as they deny this fulfillment and do not confess Christ as Messiah.
So everyone who acknowledges me before men, I also will acknowledge before my Father who is in heaven, but whoever denies me before men, I also will deny before my Father who is in heaven. [Matthew 10:32-33]
True “Jews” today are those who worship Christ as their Messiah and Lord. They worship the true God, as Abraham did. As the apostle Paul wrote:
But it is not as though the word of God has failed. For not all who are descended from Israel belong to Israel, and not all are children of Abraham because they are his offspring, but “Through Isaac shall your offspring be named.” This means that it is not the children of the flesh who are the children of God, but the children of the promise are counted as offspring. [Romans 9:6-8]
Know then that it is those of faith who are the sons of Abraham. And the Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel beforehand to Abraham, saying, “In you shall all the nations be blessed.” So then, those who are of faith are blessed along with Abraham, the man of faith. [Galatians 3:7-9]
Islam was born out of a lie told to a false prophet in the Arabian desert. One might as well say that Mormons worship the same God because they claim to worship the God of Abraham. In fact, the god of Islam claims: Christ is not divine (S. 5:116), was not crucified (S. 4:157), and the Trinity is a damnable lie (S. 5:73). Why would the God of Christianity teach other people complete opposite things? This is contradictory not only to the word of God, but simple logic.
Like it or not, Muslims and the disbelieving Jews of today are not worshiping the same God. This is what the word of God itself says, as well as just plain logic. A person might not like this and may say it’s mean, or repeat “But the pope said…” ad nauseum, but I would invite them to interact with the passages presented here.