I disagree. You are assuming that people must follow a religion, and that leads you to compare the peacefulness of one religion to another and than conclude that because all of them are not very peaceful, then there is no point to question Islam. However following a religion is not a mandatory requirement, as plenty of atheists have shown. If the question was "How healthy is vegetarianism?", then you could've been excused to compare the health benefits of being vegetarian vs eating meat. After all, eating food is a basic necessity and there are just so many types of foods, but that's not the case with religion.
If you really must make a comparison, than think of the question in this way: "Is there anything in Islam that would cause an avid follower to become more or less peaceful, compared to the same person if he/she didn't care about Islam?"