I came to this discussion late but feel I have something to add...
As a general dentist nearing the end of my career I am very glad I did not become a specialist. Some of the things I enjoyed most in my professional life revolved around VERIETY. For example, over the years I have been able to ply my craft in 8 states and 3 counties. I have worked in clinics, offices, schools, churches, prisons, hospitals, and theaters. I have taken care of condemned murderers and international heroes. I have worked with the newest of new equipment and techniques and I have worked like a dentist in 1920. I have been an Owner, an Associate, an Employee, an Independent Contractor, a Partner, and a Volunteer. I have worked at various times and places because I was paid well, because of a sense of duty, because it was novel and/or fun, and a few time because of a call from God. I have been able to drop everything and take a sabbatical from dentistry twice.
Had I become a specialist I feel my options in my profession and my life would have been narrowed.