Michael Horton preaches the gospel (albeit imperfectly); the FVers do not.
We can discuss what is being said here. Some would even advance that the FVers preach the Gospel (albeit imperfectly). Both groups adhere to the gospel as defined in the narrow sense and as lined out in 1Corinthians 15:1-8.
1Co 15:1 Now I would remind you, brothers, of the gospel I preached to you, which you received, in which you stand,
(1Co 15:2) and by which you are being saved, if you hold fast to the word I preached to you—unless you believed in vain.
(1Co 15:3) For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures,
(1Co 15:4) that he was buried, that he was raised on the third day in accordance with the Scriptures,
(1Co 15:5) and that he appeared to Cephas, then to the twelve.
(1Co 15:6) Then he appeared to more than five hundred brothers at one time, most of whom are still alive, though some have fallen asleep.
(1Co 15:7) Then he appeared to James, then to all the apostles.
(1Co 15:8) Last of all, as to one untimely born, he appeared also to me.
One group says that the Gospel commands and promises and the other denies that there is command (that is the job of the Law). Both do it on a level that seems harmful to me. There is Gospel obedience and Gospel repentance. Depending on what strain of FV you are speaking about justification by faith alone is not an issue. I know a lot of FV guys who believe that. Even if they have problems with imputation. A lot of others have fallen into the New Paul Perspective. The FV movement was not as monolithic as you are painting them. A lot of the FV issues had to do with sacramentology and how they viewed Covenant Theology. Some of it had to do with imputation. So the Federal Vision issue was quite complex. When one says that the Gospel doesn't command anything and that it is just a victory message we ought to have just as much concern with that as we do with problems concerning Federal Vision doctrines of Imputation, Sacramentology, and Covenant Theology which has been reduced to mono-covenantalism. When they want to declare that "Gospel obedience" or the "Law turned into Gospel" is "serious error" we ought to be concerned. Do I need to remind others that this has happened on this discussion forum by others in the past? The reaction of the swinging pendulum has gone past where it should in both instances. That needs to be recognized.