Bronchial infections can be viral or bacterial in nature. Just depends. Sometimes, a low-grade sinus infection can progress to bronchitis. Even viral bronchial infections are often treated with precautionary antibiotics, simply because the mucus in the bronchial tubes is such a welcoming host for bacteria that will need antibiotics to treat. So it's better to get them out of the way to start with.
Bronchitis is no fun, no matter what causes it. It's uncomfortable at best and downright miserable at worst. You may wheeze for weeks, and have a nagging cough for months after a really robust bout with it.
Even when you're over the infection, do have the doctor listen to your chest every couple of months, just to make sure the bronchitis doesn't mount a comeback.