Judaism VS. Christianity

I wonder why Jewish religion needs to be relevant in the 21st century when its son, Christianity has matured and able to provide for the same set of faith based values. I fine Jewish religion to be like Windows operating system while Vista is running all the major computers. With say no more that 20M people still clinging to that way of worship while over 2 Billion follow the newer version is it realistic to hedge world security on it? I know some say its the principle of the matter that we must fight for and not let rights of people be trampled.