More specifically, the difference between radical Islam and radical Christianity is simply the difference between martyrdom and murder.
If you look at international news, chances are you will see an example of a follower of Islam killing someone else. You have suicide attacks in Israel, terrorist beheadings in Iraq, bus bombings in England, train bombings in Spain, etc.
If the media reported it you would also see examples of Christians dying for their faith. There are believers being run over by steamrollers in North Korea, shot in China, burned alive in Vietnam, beaten in Pakistan, put to death in Iran, etc.
Except for the lone Christian cultist you do not see examples of Christians going out to murder in the name of Jesus. When there is a crazy who claims to be killing for Christ, the Christian community as a whole denounces the individual and his actions.
What you do see is Christians willing to die (not kill) for their faith. Yesterday at our university’s December graduation we had a Christian leader from India give the keynote address. He has had 18 attempts on his life because of his beliefs. He was set to speak somewhere and the police told him he couldn’t because they thought there was a bomb under the stage. Five minutes later they found the bomb. He has said that he is not seeking it, but it would be a privilege to die for Christ.
Compare that to the jihad of Islamic extremists. There are countless examples of Muslims killing in the name of Allah. Then after the attacks, few are far between are the rebukes from fellow Muslims. Usually the victim is responsible somehow. Be they American (“because the war”) or Jewish (“because they…were born”), the majority of Muslims seems to look the other way when fellow Muslims murder.
You may say that both want to outlaw [insert your pet issue considered a sin by both religions], but the difference is your Christian neighbor is not going to behead the gay guy living across the street. The Muslim in Sri Lanka may kill the woman down the street because they dared to walk out of the house with more than their eyes showing.
Any comparison between two groups can be made and justified somehow. Everyone shares some type of common belief with basically everyone else. But ask yourself two questions if you are neither Christian nor Muslim: Do you feel your life is in danger here in “the West” because you are not a Christian and don’t live by the Christian value system? Would you feel your life was in danger in the Middle East if you were not a Muslim and didn’t live by Islamic law?