Part of the reason for the disparity (I am not contending it has always been that way, so anyone wanting to bring on the Spanish Inquisition, please save it for another thread) is that the Christians are more isolated in their violence. In other words, they do not have figures of authority in their religion egging them on. Muslims do.
Apart from rare nutters like the Westboro family I cannot recall any Christian murderer who is adored by Christians because he is a murderer.
But many Muslims adore Bin Laden, not because he is a great scholar but specifically because he murders infidels.
However, do note that a few cases of Christians advocating violence and acting still exist:
In spring of 2009 three American clergy visited Uganda to help its churches seek revival and to specifically discuss “the threat homosexuals posed to Bible-based values and the traditional African family”.
These three American evangelical Christian pastors were headlined as American experts on homosexuality.
One month later, the aftermath of their visit was a rather literal interpretation of one of their messages: ‘…the wages of sin are death’. Almost immediately calls went out for homosexuals to be put to death. To be put to death by law.
The American pastors identified what they believe to be a cause of Uganda’s raging problem with AIDS/HIV: homosexuals; even though the evidence is that most Ugandan carriers are heterosexual and infected through infidelity.
Now in early 2010, with church support, a law has been proposed that anyone that knows a homosexual and does not turn them in will be imprisoned.
http://bill4dogcatcher.wordpress.com/2010/02/10/death-to-gays-says-ugandan-christian-church/
The blogger continues (and sounds very Christian in doing so):
The way I see it: if God actually has a plan for each of us and is our creator then we are are all his children. When Jesus brought the good news and taught on the mount, Jesus extended God’s grace to all. We should too. We are all God’s children.
Words matter. If the wages of sin are death then there are several lists of deadly sin in the Bible … but as Jesus taught us: ‘Let him who is without sin cast the first stone.’
In one blog entry the man teaches us both that Christian violence exists and that a real Christian cannot actually support it.
Both lessons are missing in comteporary Islam. Islamic violence is rarely acknowledged by Muslims and very often justified by those that do acknowledge it.
(Plus there is the weird case of those who acknowledge the violence, condemn it in general, but make certain exceptions like for "resistance against occupation" where immoral acts are suddenly moral proving that in their worldview morality is not absolute but depends on politics alone.)
To be fair, American Christians do condemn this outbreak of violence in the name of Christianity:
In a case of strange political bedfellows, conservative Republican Senator Tom Coburn of Oklahoma has joined leftist comedian Al Franken, a Democratic senator from Minnesota, in sponsoring a bill denouncing Uganda’s Christians for considering passage of legislation to outlaw certain unhealthy and immoral homosexual practices
http://www.worldtribune.com/worldtribune/WTARC/2010/af_uganda0114_02_12.asp
"Christianity Today" reports:
The proposed anti-homosexuality legislation in Uganda has created tension between American Christians who have condemned the legislation and Ugandan Christians who don't want to see homosexuality become an acceptable practice.
Several American pastors and leaders have condemned legislation in Uganda that, if passed in its proposed version, would punish homosexual acts between adults—including touching "with the intent of committing the act of homosexuality"—with life imprisonment. The punishment for "serial offenders," homosexual sex with minors or the disabled, or homosexual sex while being HIV-positive, is death.
http://www.christianitytoday.com/ct/2009/decemberweb-only/151-41.0.html
But while there are scholars who acknowledge violence against non-combatants and outside self-defence and regardless of who the enemy is, they are considerably rarer in Islam than among Christians.