Circleci/python:3.6.1-browsers vs selenium/standalone-chrome:3.1.0



I am just starting with the CircleCI and 2.0 and I would like to know what is the recommended way to do UI integration testing. I see that python demo app uses separate image for selenium/standalone-chrome:3.1.0.

Is this recommended vs circleci/python:3.6.1-browsers? I tried circleci/python:3.6.1-browsers, and i am able to run my UI tests. What is the difference? Why and when should I use one or another.