Is the love between husbands and wives any different from the love fellow Christians have for each other or for non-believers?
Greek has three basic words for love, two of which are used in the Bible:
Agape is a devoted love. It gives even when it is not returned. Agape is a love done on purpose; it is chosen. This is the type of love that we are told God had for mankind. "But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us" (Romans 5:8). This is the type of love described in I Corinthians 13:4-8; the type of love that Christians are to have for each other. It is also the type of love that husbands are to have for their wives. "Husbands, love your wives, just as Christ also loved the church and gave Himself for her" (Ephesians 5:25).
Philio is the love of companions. It is what you have with your best friend. Interestingly, while husbands are told to love (agape) their wives, wives are told to love (philio) their husbands and children. "That they admonish the young women to love their husbands, to love their children" (Titus 2:4).
I believe the difference is due to women being more emotional in their relationships. Men can often act despite their emotions at the moment. Women generally act because of their emotions. Because husbands are to lead their homes, it requires making decisions and acting regardless of his current emotional feelings. Thus when a disagreement occurs between a husband and wife, it is the husband's responsibility to do what is right -- to express his love for his wife -- regardless of any bitter feelings of the moment. God made woman to be man's companion (Genesis 2:18; Malachi 2:14). Thus a wife's love (philio) for her husband is the fulfillment of her role.
All Christians, male or female, are to demonstrate the agape type of love to each other. People can be annoying at times, yet we must choose to show love for one another regardless of our current emotions toward that person at the moment.
The third Greek word for love, which is not found in the Bible, is eros. It is the word for romantic or sexual love. While husbands and wives display a sexual passion for each other (I Corinthians 7:1-9; Proverbs 5:18-19), it does not serve as a foundation of the relationship. It is a pleasant benefit to being married, but it does not define marriage.
You mention the love Christians ought to have toward non-believers. While we should be concerned for the souls of everyone we meet, not willing that any should perish, yet the Bible warns us not to build close ties with those who chose to remain in the world. "Do not be unequally yoked together with unbelievers. For what fellowship has righteousness with lawlessness? And what communion has light with darkness? And what accord has Christ with Belial? Or what part has a believer with an unbeliever? And what agreement has the temple of God with idols? For you are the temple of the living God. As God has said: "I will dwell in them And walk among them. I will be their God, And they shall be My people." Therefore "Come out from among them And be separate, says the Lord. Do not touch what is unclean, And I will receive you."" (II Corinthians 6:14-17). Or, as John put it, "Do not love the world or the things in the world. If anyone loves the world, the love of the Father is not in him" (I John 2:15). The Greek word for love here is agape. A Christian cannot choose to devote himself to those in the world. He will compromise his principles and destroy his relationship with God.