It’s a great question. What if both religions are true? If you seperate out what both Jesus and Muhammad taught as opposed to the disparate beliefs held by their followers there will be much more consistency between the two Revelations. One major problem with both religions is they emerged during historical circumstances very different from today. To understand both the Bible and Quran requires a deep understanding of both textural and historic context.
Islam essentially teaches is that Christianity
is true but that its original essence has been distorted over time due to religious 'exaggeration' on the part of its adherents, leading them to declare Jesus to be God (Qur'an 4:171, 5:116, 9:31, etc.); so, if I became a Muslim, then that is the position I would naturally adopt. Or are you asking that I consider your religion, the Baha'i Faith? I already have, and I have my own reasons for rejecting it. I am skeptical of all such syncretic attempts to subsume all the major world religions into some kind of artificial unity. To do this is in fact to separate these Traditions from their context, not to realize them within it. You affirm the truth of these religions in a general sense, but do not realize exactly what that entails. A good example is the finality of Muhammad's prophethood in the case of Islam (cf. Q. 33:40). Baha'is do not seem to realize just how essential this teaching is to Islam's understanding of itself. The central teaching of Islam is submission to the One God (Q. 6:71, 112:1-4, etc.) who has sent numerous prophets to guide humanity towards this (Q. 16:36). However, each time, the people turned astray and corrupted the message which was entrusted to them (Q. 2:75-79, 3:77-79, 187, 5:13-15, etc.). Therefore, God sent one final prophet (Q. 33:40) whose message would be for all of mankind (Q. 21:107), and which would confirm the truth which was previously revealed to them (Q. 2:41, 89-91, 101, 3:81, etc.) and right that which they had altered, and God would ensure that this message would be preserved until the end of time (Q. 6:115, 15:9, 41:42). That's as simple a summary of Islam as I am capable of, and from this it is quite clear that the
literal finality of Muhammad's prophethood is simply so integral to the fabric of Islam, at least as I understand it, that without it, you've deprived Islam of much of its meaning. Another example is how Shoghi Effendi claims that, in the Baha'i Faith, "the primacy of Peter, the Prince of the Apostles, is upheld and defended" (
The Promised Day is Come, p. 109), but what does this even mean anymore if you discount the entire Catholic Tradition and the promises made in Matthew 16?