It is hard to generalize about the pros and cons of unions because there are so many different unions and locals. Though union membership has declined, there are some signs of renewed interest in union membership.
Pro 1: Unions increase pay and benefits for workers.
Through the process of collective bargaining, unionized workers are able to secure higher wages and better benefits, like pensions. Employers hiring for non-union jobs have to increase their wages, too, in order to compete for employees.
Pro 2: Unions set up formal processes for disputes and complaints.
Formal processes make it easier for workers to raise grievances. Many unions subsidize legal fees for members who want to sue their employers, such as for discrimination.
Pro 3: Unions make political organizing easier.
Unions empower the members’ political voices to advance political causes that working people support. They help keep candidates focused on relevant labor issues.
Pro 4: Unions set norms that extend to the rest of the economy.
Unions brought certain norms to the benefit of even non-unionized workers, for example the minimum wage, safety guidelines, and overtime pay.
Con 1: Unions can make it harder to promote great workers and get rid of not-so-great workers.
Unions value seniority, which is good for creating a steady career path, but it can hurt younger workers trying to advance their careers. Seniority also protects workers who consistently under-perform.
Con 2: Unions can require dues and fees that some workers might not want to pay.
Some unionized workplaces fall into three categories:
These formats are unfair to people who don’t want to pay dues or fees. Some critics of unions prefer open shops, where employees can’t be required to pay dues or fees.
Con 3: Unions can lead to a closed culture that makes it hard to diversify the workforce and weed out bad actors.
Unions also have distinct cultures, which vary by union and by “local.” The closed cultures of some unions can make it hard for outsiders (e.g., women or people of color who want to be union welders) to advance. It can also lead union members to cover up member misconduct.
Con 4: Unions can drive up costs and lead to an adversarial relationship between labor and management.
Unionization leads to higher labor costs. Union labor, which the government sometimes requires, can make big projects (e.g., building a new subway line) much more expensive. Unions sometimes lead to hostilities between labor and management.
Source: The Pros and Cons of Unions