Being from the CS department, I can give you a list of pros and cons about the department, and hopefully if people from the other departments do the same, you can form your own conclusions about the “best” department.
Pros
1) Most faculty of the department are friendly and approachable.
2) There is no red-tapism in the department. You get to meet and talk to most professors any time you walk into their office without fixing an appointment, unlike some of the other departments. Back in my second semester, one professor in the Chemistry department asked me to get out and first fix an appointment when I went to his cabin for some reason.
3) The majority of the department (including the students), in my opinion, is more motivated than some of the other departments. There is a lot of energy amongst the faculty to publish quality papers in a variety of areas that are currently considered “hot”, and some undergraduate students too are getting involved with faculty in their projects and research work, and publishing papers in good conferences.