I've always believed (like Christians around me) that Christ's Bride is the church. However, I recently met two guys that claimed that the Bride is actually the new Jerusalem that comes down from Heaven in Revelation (3:12, 21:2, 21:10). What is the Biblical support for these two viewpoints?
The new Jerusalem that comes from heaven in Rev 19 is "prepared as a bride adorned for her husband." (emphasis added) However, I would understand why some might think that Jerusalem is Christ's bride. In the Old Testament, Israel (or Judah or Jerusalem) is described as God's wife:
This comparison is the whole purpose of the book of Haggai as well. It's a beautiful way to render God's relationship with his people.
Contrastingly, the imagery that we have with Christ and His Bride is that of a coming Bridegroom and a bride in preparation. As the angel shouts in Revelation 19:7
Paul strengthens this image when he says in II Corinthians 11:2
The two metaphors are not contradictory. Jesus uses many contrasting "I ams:" Jesus is the Lamb, the Door, The Good Shepherd, etc. All of them are helpful, but they are only pictures. HOWEVER, this imagery of Christ and His bride persists through all the New Testament, especially in the Revelation. It is meant to typify how an engaged virgin would wait for her promised husband to come for her. That is what Christians are doing today. God was never married to a city. Jesus is not coming back for a city. The city always was a symbol for the collective people of the city, and the Bride is a metaphor for all the Christ's body.
There's no reason why God couldn't use a "bride" analogy two places in different contexts. If one day I say, "Bob works as hard as a horse" and another day I say, "Charlie can run as fast as a racehorse", that's not a contradiction because I compare two different people to horses, or compare them in two different ways. Even if it's true that God refers to himself as having two different brides, that doesn't make him a bigamist! Neither is literal, it's just an analogy.
That said, New Jerusalem is to be the home of the saved. The Church is the collection of those who are saved. So both are pretty much the same group of people.