You get a chance to meet the director as well as all the managers (one of which will end up being yours). If it is just one person interviewing they have all these people in one room along with you. If there is a group, each manager along with the director will be in an office where you will get a chance to 1 on 1 with each of them individual and you will be a in rotation with the other candidates. Solo or group, you will have a written interview in addition to the in-person interview. The written interview will take you roughly 30 minutes to complete but you are given 1 hour. I still recall all the questions.
Solo interview takes no longer than 2 hours. The group interview will take you the whole day where lunch is usually provided.