Which state's insurance adjuster license is the most useful to get (best for reciprocity)?

Florida and Texas are the most useful for reciprocity. They are the only two states that issue designated home state (DHS) adjuster licenses, and with either one you can obtain licenses in other states by application and fee alone, without retaking each state's exam. California, Hawaii, and New York do not reciprocate, so those states require their own full education and exam process.