Now, little children, remain in him, that when he appears, we may have boldness, and not be ashamed before him at his coming.
In all of these passages and a dozen others like them in John's letters the meaning is identical.  Could there be any conceivable difference between one who was abiding "in the light" and another who was abiding "in the word of God," or "in God," or "in Christ," or "in the Holy Spirit?"  Conversely, could there be any distinction between persons "walking in the truth" (as in  3 John 1:1:3) and those in whom the "word of God abideth"?  Again, reference is made to a more lengthy study of this phenomenon in my Commentary on Galatians, pp. 97-99.  In full consonance with the unity of thought in all such passages is the over-all consideration that every single one of them means, in the last analysis, believing and obeying the commandments of God, a fact inherent in the very next verse where John spoke of "doing righteousness" as evidence of one's having been born again.