So-called "permanent replacements" (also called "strike breakers" & "scabs") are only permanent if the employer succeeds in breaking the Union or creating circumstances where-by the strikers would accept a contract which did not require returning the jobs to their original holders.

Unions provide job security by insuring that any termination adhere to the "Seven Standards of Just Cause" rather than the whim of some manager. Many unions also have a Seniority Clause which increases an individual's job security as their time on the job increases.

If you truly did not want to start a debate, you would not have made such a biased statement as "The only thing that is certain with union representation is that you will pay union dues". With Union Representation, you are certain that every article in your contract, including salary and raises, sick leave, vacation, etc. will be strictly enforced.