The rule of thumb
If the hardware is sound and you only need old keys dead — rekey. If the hardware is worn, corroded, ugly, low-grade, or you want different function (keypad, lever, higher security) — replace. Rekeying changes who can open the door; replacement changes what the door is.
When rekeying wins
Move-ins, lost keys, roommate and staff changes, post-contractor cleanup, and keying every door alike. It's fast, cheap relative to hardware, and preserves finishes that match your house.
When replacement wins
Locks that bind even with a good key, visible pitting or rust (coastal homes age hardware fast), builder-grade knobs guarding a street-facing door, or any move to smart or high-security hardware. A rekeyed worn lock is still a worn lock.
The hybrid nobody mentions
You can replace the cylinder alone in many commercial and some residential locks — new keying, new security level, same body and trim. Ask about it when the lock body is good but the keyway or cylinder isn't.
Cost logic without numbers
Rekeying is priced per cylinder and scales gently across a whole house; replacement is priced per lock and scales with hardware grade. Which is 'cheaper' depends entirely on what's on your doors — which is why a phone quote describing your actual doors beats any price chart on the internet.
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Niceville Lock & Security Guide — independent local guidance for Niceville, FL. Questions a guide can't answer? Call (850) 616-0859.