Oh, David and Co. were certainly saved but we are the very fortunate recipients of the permanent indwelling of the Holy Spirit, who men of old longed for but who only came upon them at certain times.
They had their wives and concubines, we have the comfort of the Holy Spirt who shows us the beauty and grace of Christ and the love of God.
Who came out better? Us I think.
A point of curiosity for me, which may get clarified in the next life, is which OT saints had extended visitations by the Spirit:
Abel?
Enoch?
Noah?
Job?
Abraham?
Moses?
David?
Elijah?
etc.Daniel?