I recently posted about the pros and cons on my website but to answer your questions they are quite different. Small groups have some risk associated with them. If one person calls in sick there are fewer people to pick up the slack. Negotiations with insurance companies can be more difficult since you don't have a lot of "weight" behind you with a small group. Small groups also may be one financial purchase or write off away from a disaster. Suddenly that urgent care center that was supposed to be a cash cow might be a huge loss that the group could not support.
The benefits of being in a small group, for me, outweighed the drawbacks. I joined a small independent group and I love it. I was able to offer suggestions my first month of being on the job and many of them were welcomed and enacted. Changes with the group are easy to come by since there are only a few members and we can easily have a quick vote if something needs to be changed. I've noticed that there is much less bureaucracy being with a small group and not a large organization. I answer to the group and even though the hospital administration will offer their opinion, I feel like I am free to practice medicine without a CEO who has no clinical experience telling me what to do. Salary was another benefit. Since the small group is employee owned and employee (physician) run, everything that it does is arguably in everyone best interest. We all have the same pay structure, same schedule with no priority, same rules to abide by, and a generous 401K plan.
Overall I think you need to see what the culture is like at any group you interview with, small or large. If you have a small group and do not get along with any of the people in the group, you are going to have a very bad time.