I always thought the use of paper bags would be more beneficial for the environment until I read this article about the impact of both paper and plastic on environment.
contrary to what most people think there are advantages of using plastic bags instead of paper bags. Like paper, plastic can be recycled, and recycling process would require less energy for plastic than it is for paper. Paper recycling requires the use of great amount of water and end result would be polluted water back into the environment.
please read this article which brings up important issues regarding use of paper and plastic.