Are you just an employee or also an owner in that company? If you are an employee only, having a union to back you up could be extremely useful if things ever go bad.
If he can't leverage his power when he already represents 100% of the company's employees a union is unlikely to help.
Another larger union, which organises industrial workers, cleaning staff and generally people with less formal education, is almost twice the cost. They do negotiate at least base pay for the industries they represent. Many of the people they represent are often better off having their union do the negotiations. When handling negotiations it's obviously not only about money, but the unions do need to be able to provide at least raise in salary that can cover their dues, and sometimes they can't.