The terms are interchangeable. In Maricopa County, each case valued less than $50,000 by the parties is subject to mandatory or compulsory arbitration.
Disclaimer: This post is intended for informational purposes only and is not intended to provide legal advice or establish an attorney/client relationship. Legal advice should be obtained after discussing the specific facts of your case with an attorney licensed to practice in your area.
Compulsory and mandatory mean the same thing. Courts generally give wide deferenec to arbitration awards, along with the policies of promoting settlement and honoring contracts in which the parties agreed to arbitrate.
Disclaimer: I'm only licensed in CA. Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.