I have been a government worker for more than 30 years. When I first started I was covered by a union. Later I was promoted into a classification that the union did not cover. Because of some perceived management abuses, a new professional bargaining group was formed. It was not exactly a union but it acted as one. Even later I was promoted out of the classification this group covered.
All of this gives me some insight on public service unions from the inside and from the near-outside.
I don't see a lot of benefits derived from collective bargaining. The biggest advantages to working for the government - pension, civil service, job security - existed long before public service unions could collectively bargain. Public service unions were legalized in the Kennedy administration. OPERS, the pension plan I am under was founded 75 years ago. Civil Service protections go back to the 19th century.
Originally I was covered by AFSCME. This was at the tail end of the high-inflation years of the last-1970s. I remember that we got cost of living raises every few months, which was good, but that the raises were the same for everyone. I think that they were based on average salary which meant that people who made less than the average saw their income go up faster than inflation while people who made more than the average saw their buyign power decrease. That part was bad.
A few lessons I learned from that period was that unions were more concerned with their own members than with City workers as a whole. At one point the non-uniformed and fire unions had agreed to a wage freeze because of a budget crunch. Some money became available and the administration offered to use it to give everyone an increase. The police union was still negotiating and insisted that they get all of the money.
Later, after I was promoted out of the classifications covered by AFSCME, they were trying to justify something and used the argument that management could afford it because they had been giving "top management" the same benefits that AFSCME got. I got a real laugh out of being included in the term "top management". I supervised one or two people and spent at least 90% of my time doing the same work that they did. Since then management has never quite gotten the same benefits as union members. Thanks AFSCME.
One classification had a single pay rate rather than a range meaning that everyone was paid the same regardless of performance. Management wanted to change this so that high-performers could be rewarded. The union refused, insisting that the raises would only be used to reward management's friends.
Years later the City was in a budget crunch and raises of any kind were hard to come by. To save money, the City promoted a few people to a salaried position so that they would not be paid overtime. This caused them to organize the new group CMAGE which represented professional workers. Promises were made - CMAGE would always be an independent group and it would not require a "fair share" payment. Both of these promises were broken rather quickly. Co-workers still covered by CMAGE (which is now part of CWA) would love to take their vote back.
So my personal experience with unions has not been very positive.
On a different but related subject, teacher unions are warning about increased class size if cuts are made to education. I recently found a picture of my 6th grade class. The class size was 34. It did not feel huge and I never felt like the teacher was overwhelmed and had no time for me. In fact, numerous studies have shown that smaller class size does not help the student.
So why the push for smaller classes and the scare stories about larger classes? Because larger classes are more work for the teachers. It is as simple as that.
Remember that unions exist to benefit their members (and the union leaders, possibly not in that order). They do not exist to benefit the public at large. The largest unions use part of their dues to elect candidates that will support them over the general population. This almost exclusively benefits the Democrats.