Most of the horrendous violence unleashed by various Christian sects of the centuries occurred before the advent of bombs, but if you want to talk about the cost:benefit ratio, the Christians have caused far more deaths in the name of their religion than the Muslims. Islamic terrorism is largely a result of a particular brand of fundamentalism unleashed in the 20th century. The Christian history of mass atrocity goes back centuries.
If you're asking which is objectively worse, I'd direct your attention to the genocide of every indigenous culture in South America, explicitly in the name of Christianity, as only one example of many that make Christianity objectively worse over the course of the last several hundred years. The Muslims are going to have to step their game up to even be in the same league.