It just depends on the class and the person.
I found that I was much better off in gross anatomy going into the lab with classmates because I could go through all the parts that we needed to know faster and label stuff with with much more confidence.
Outside of that, I prefer to study alone, except that I often study in a designated study area for dental students so if I or anyone else in the room needs help understanding a topic we can always ask someone else in the room.