It is, in my opinion, almost* (disclaimer: see below) better to be an unbeliever than a lukewarm Christian. Let me explain:
Picture for a minute an unbeliever, caught head-over-heels in sin, who has never heard the Gospel preached before and is generally unaware of his Sin. The Gospel is presented to him. He hears for the first time of he depth of his sin, his separation from God, how his good works are worth nothing, how he (in and of himself) can do absolutely nothing to save himself. When his need is revealed to him, he is full of despair, depressed, anguished, humbled, broken, contrite over his Sin. He knows he's wrong and could never be right before God. Then he is told that there IS a way to be saved from the horrors of his sin and the consequences that he deserves because of it. That God, the Creator of the universe, spanned time and space and reached down to save him (a poor, undeserving, wretched sinner). He acknowledges his sin, believes Christ to be the propitiation for the punishment that he deserved, and repents. How the angels sang on that day! He is SO happy, he cannot bear to keep the Good News to himself! He is on fire for God, passionate, zealous, constantly desiring to learn more of God. He cannot hear enough about Him. He devours every book he can get his hands upon, desiring to learn all that he can about Him. He constantly grows in relationship with God. He is in continual awe of this Creator-God, who spanned the gulf to rescue him, the lowest of the low!
Contrast that with the disgusting image of a lukewarm "Christian"- Possibly one who grew up in the Church, who knows "everything" there is to know about God- full of knowledge, but void of a real relationship with God (that which really matters). He is numb, passionless, apathetic, ineffective, useless, deceived, self-sufficient, even hampering the spread of the Gospel by his hypocrisy and contradictory witness/lifestyle. His "worship" is empty, hollow, half-hearted, and lifeless. He is overly familiar with the Church and is bored by its traditions, rules, and rituals. He is legalistic and lives life by the rulebook. He can quote the Bible, Church fathers, and theologians left and right. He goes to Church, listens to the "good" music, reads the right books, has Christian friends. It all looks perfect on the the outside, but on the inside... He says that he believes in Jesus, but his life (choices, decisions, values, character etc) screams otherwise. It's all head (knowledge) and not heart (real wisdom).
Again, it is almost* (disclaimer: see below) better to be an unbeliever than a lukewarm "Christian"
"I know your deeds, that ou are neither cold or hot. I wish you were one or the other! So, because you are lukewarm- neither hot nor cold- I am about to spit you out of My mouth... You do not realize that you are wretched, pitiful, poor, blind and naked... Those whom I love I rebuke and discipline. So be earnest and repent! Here I am! I stand at the door and knock. If anyone hears My Voice and opens the door, I will come in and dine with him, and they with Me." - Revelation 3:14-20
"'By their fruits you shall know them.' (Matthew 7:16a) You say, 'Wait a minute, I thought we were saved by grace through faith and all of that.' That's right, we are. But whether we are saved or not shows up in our deeds. James says the same thing (James 2:14-26 Your faith is made known by your works. So He says I know your deeds and therefore I know your heart. I can see by what you do who you are," says John MacArthur.
"But I submit to you that Jesus said, 'I would rather have you cold than this. I'd rather you be a prostitute than a Pharisee. I'd rather you be a sinner who knows his sin than a hypocrite who doesn't recognize it. I'd rather you say... God, be merciful to me, a sinner...who feels the coldness of his lostness than a Pharisee who says I thank You I'm not like other men.' Anything is better than lukewarmness!" - John MacArthur
"But there was something worse than being lukewarm and that was their self-deception. They had spiritual pride. They thought they were spiritually rich. They had attained spiritual knowledge. This is the hardest person to reach. The intellectual apostate, the intellectual unsaved hypocrite who stays in the Church. They are religious and damned. This is a person to be pitied." - John MacArthur
"They profess to know God, but in works they deny Him, being abominable, disobedient, and disqualified for every good work." - Titus 1:16
"What good is it, my brothers and sisters, if someone claims to have faith, but has no deeds? Can such faith save them?... Faith by itself, if not accompanied by action, is dead. But someone will say, 'You have faith; I have deeds.' Show me your faith without deeds and I will show you my faith by my deeds. You believe there is one God. Good! Even the demons believe that- and shudder! You foolish person, do you want evidence that faith without deeds is useless? Was not our father Abraham considered righteous for what he did when he offered his son Isaac on the altar? You see that his faith and his actions were working together, and his faith was made complete by what he did... You see that a person is considered righteous by what they do and not by faith alone... As a body without the spirit is dead, so faith without works is dead." - James 2:14-26
* Disclaimer- I say "almost," because if a person was genuinely saved, there is always the chance that they have just wandered from the Faith for a time and will be back. In the case of the die-hard unbeliever, there is always the chance that they won't hear the Gospel... In which case, it would be better to be the lukewarm Christian...
Argument developed by myself. John MacArthur quotes taken from a sermon entitled "Laodicea: The Lukewarm Church" (Parts I & II) over Revelation 3:14-20 on 03.06.1992. Found at: http://gty.org/Resources/Sermons/66-14
