Personally, I use classes over id’s all the time. Reason why is it keeps things consistent along with the fact if you need to add any type of jquery etc. to that div, you may need to use an id and since you can’t use multiple id’s on a div/section like you can with classes, it is best to just use classes. Once you start using both for pure styling, you may come across some issues because id’s take priority of classes so at times maybe some of your style get overwritten due to the id styles.
Like the post above me, Bootstrap uses pretty much all classes. We use bootstrap here and love it so it works out since we do classes.