The world would be better off without any religions. It's 2015, we've been to the moon, we can cure serious diseases, we have fantasic advances in science, yet people cling to these silly ancient texts and backwards views of the world.
It's very very scary.
I do think people would still kill each other, but it would be based on acquiring what other have or quashing a political movement, no because one person worships the wrong invisible man living in the sky.