I think you are the first on this site to ask me this. I have answered this in the past but it goes unnoticed. There is a huge difference. One, like the thief on the cross, who became an object of Christ love and mercy, yet lived the life of a thief, will stand at that 1st. Cor. 3 judgment seat. A failing Christian will not be there to determine “who he is” or “where he will go.” That is not the purpose of the judgment.
The fact that a “believer” stands at this judgment, only shows he is a family member already. It is an exclusive judgment only for the family of God. All outsiders will be judged at the Great while throne judgment, one-thousand years after this one.
He will probably be likened to the analogy of “straw.” He lived only for self. He buried his talent,… he refused to learn of Christ… he refused to go through the narrow gate leading to life… He will be judged, NOT according to sin!.. but according to what he did or failed to do in regards to the kingdom of God as a believer. Yet, because of God’s love and mercy which is everlasting, he will pass through this judgment to enjoy his free gift in the house of God. Will he inherit anything? NO… nothing.
But the man who left houses and lands, and brother and sister and even denied his own life, will also stand at the same judgment to give an account. This is a man who sanctified himself by dying to self and living to Christ. His reward will be great. He will rule over nations.