The short term benefits of plastic are that it is cheap to make, so companies save money with packaging things with it instead of using alternatives. In the long term, plastic can be used for so many things, so as long as we have scientists we will have new ways to use plastics.
A short term negative benefit would be that plastic isn't good for our environment. A long term negative benefit.. plastic doesn't decompose like other things humans use. A plastic bottle for example will be on Earth for 450 years. It all adds up.
