Deadbolt is definetely safer than door knob because deadbolt has a dead latch that cannot be retracted or slim jimmed. In order to unlock a deadbolt, someone has to have original key that will turn a cylinder and move long shaft that goes inside a frame and allow to open the door
While door knob has a latch that is spring supported and can easily forced to get it unlocked.
There are many more options to secure the house such as hidden deadbolt or guard plate.
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