I struggled with this very issue for years but the Holy Spirit directed me again and again to this question: "How can you say you love me and have not love for others that believe in Me". This thread poses an excellent question for me as a Christian.
The Bible is very clear about being unequally yoked with "Unbelievers"--Those that have left the faith and those that do not believe in Christ Jesus; not denominations. The wrong interpretation of what is correct/incorrect doctrine being taught concerning the Word can destroy and prevent potentially great fellowship/marriage with other true believers in Jesus.
The only place in scriptures that I have found where Christians are to reject fellowship with an individual is if that denomination teaches doctrine classified as "Doctrines of Devils". 2 King James Bible (Cambridge Ed.), John 1:7: "For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist."
My hang-up in the past was concerning doctrine centered on the Godhead; I can only imagine that the thread indirectly is addressing similar differences; e.g., "Doctrinal" differences between Christians of different "Denominations".
King James Bible (Cambridge Ed.), John 14:1: "Let not your heart be troubled: ye believe in God, believe also in me." This question settled my concerns forever with individual beliefs about the Godhead. When considering "denominational-isms", everyone that I have met that profess to be a Christian does believe that Jesus came in the "flesh". John 14:21: "He that hath my commandments, and keepeth them, he it is that loveth me: and he that loveth me shall be loved of my Father, and I will love him, and will manifest myself to him."
Jesus is very clear in John 14:21 when he states “that it is He, that will reveal himself”. It is not for me to judge others concerning if they understand the Godhead. It is for me-- to love Christ and keep His commandments and fellowship/assemble with others that are doing the same. By loving those that love Jesus, the world will know that we are of Him because we show forth the same love that He has for us.
The only Spiritual difference or reason I would not marry someone is if she did not believe that Jesus came in the flesh. Under those circumstances and only under those circumstances would I not switch denominations. Personally, if and when I meet the Christian woman of my dreams, and should decide to get married; hopefully, we would love Jesus enough to dialogue like adults and let our decision to marry be founded on what the Word says.