Fleshly birth made citizens of David’s kingdom; a Jew must be born again to be a citizen of Christ’s kingdom.
Every child of Hebrew parents was in David’s kingdom; children must be old enough to voluntarily accept Christ to be in the future kingdom.
David was king, family of Aaron were priests then; Christ to be both King and Priest.
Some rather unruly men were helpers in David’s kingdom; only true and tried Christians are to reign with Christ. (Here the future kingdom as outlined by its advocates radically differs from David’s kingdom.)
David’s kingdom was constantly beset by its enemies; no enemies to the future kingdom.
David’s kingdom constantly organized for war; nothing like that in the future kingdom.
In David’s kingdom they learned war; in the future kingdom they shall learn war no more.
David reigned while the devil was loose and doing his worst; we are told that Christ cannot begin his reign till Satan is bound.
Moses was the lawgiver of the old kingdom; Christ is to be the lawgiver for the future kingdom.
And that is not all; but we grow weary of the task of enumerating the differences. Yet we are told that, if there is any alteration, the throne of the kingdom cannot be the throne of David.