We highly recommend you get paintball goggles that cover your ears. Although the chance of getting hit from the side is lower than from the front, it still exists, and if a paintball does hit your ear, you’re in for a possibly serious injury.
This is one feature we don’t recommend you skimp out on. Take note of the fact that ear protection can block out a lot of the noise from your surroundings. As such, when choosing a mask, consider if it has an ear foam that allows good sound transmission.