Seniority systems are beneficial mainly because they improve loyalty, stability, and predictable administration within a workplace. Based on common practice and expert summaries, the two strongest benefits to select are:

• They encourage employee loyalty to the employer.
• They provide a defense against employment discrimination claims (by basing decisions on tenure rather than individual biases).

If you’d like, I can tailor these to a specific industry or organization size, or discuss potential downsides to weigh against these benefits.