Why are there so many church denominations? Unsaved friends complain about the multiplicity of church denominations. Are some better than others?
You ask two questions. In some, perhaps most, cases, the answer to the first question lies in sinful human nature, expressing itself in contrary ways. On one side of an argument that will lead to a church split are carnal leaders who are careless about the “faith once for all delivered to the saints” (Jude 3). Opposing them are believers who refuse to accept sloppy doctrine. Sooner or later irreconcilable disagreements about the meaning of Scripture lead to a church split and church splits have in the past led to the formation of new denominations.
Some divisions become virtually unavoidable and may be said to be good. Conscientious, well-instructed members desire to contend for the apostolic faith, and some new denominations have developed in order to emphasize a doctrine or practice that was marginalized or ignored in the church from which they seceded. Baptist churches emerged from churches that baptized infants; Pentecostal churches from groups that did not pay enough attention to the Holy Spirit, etc. Of course, for the purposes of space, this is a very simplified description.
If your friend is a serious person, as he explores different churches or denominations he will not be offended by differences; instead, he will be amazed by the similarities, especially the almost universal adherence to the great, historic creeds. Sooner rather than later, your friend will find a company of brothers and sisters with whom he shares a common life in Christ, and a common creed.