Prokofiev's Spanish wife (his first wife) went to a prison camp in Siberia sometime after Prokofiev was trading her in for a younger model. I don't know the details but maybe that's why Shostakovich is reported to have said that Prokofiev had the "Soul of a goose." Sooner or later Stalin had to crack down on everybody no matter how innocuous their music just because he was Stalin and had to show that he was in charge. In any case, as much as some of Shostakovich shows the influence of Prokofiev, they were very different composers. As much as Shostakovich adopted some of Prokofiev and Stravinky's "modern" sound, Shostakovich was still full of sad Russian soul like Tchaikovsky or Rachmaninoff. Shostakovich's feelings are never far from his music, whether those feelings be sadness, sarcasm, ironic humor, or anger. Those who love Shostakovich, love him for it, and others dislike Shostakovich for the same reason. Perhaps those who don't like Shostakovich are along the lines of some others who don't like Mahler. They find Shostakovich to be be too emotional, too neurotic, too long-winded, and too morbid. So with Shostakovich, you get in his musical vision the crushing of the spirit by the hammer of totalitarianism. Prokofiev, on the other hand, is all about the music. With Prokofiev, it's about the craft, about making the waltz in Cinderella sound dream-like; like making the Classical Symphony sound modern but also completely in line with Haydn; and about making the Violin Concerto #1 sound athletic and dazzling. His friend and fellow Russian emigre, Vernon Duke, who befriended Prokofiev in America, said that Prokofiev pretty much sold his soul to the devil by returning to the USSR, but if it bothered Prokofiev at all he didn't allow himself to show it very much in his music like Shostakovich did. As for Khachaturian, he's the little brother to Prokofiev and Shostakovich. Proko and Shosty are the twin towers of Soviet-era Russian music, and Khachaturian stands beneath them. Even so Khachaturian is first among the second tier as he stands out among the likes of Myaskovsky, Kabalevsky, and the other Soviet composers whose works are by-and-large unmemorable. Khachaturian's wonderful Armenian-flavored Violin Concerto is interesting enough that James Galway transcribed it for flute, so if Galway is going to go through all the trouble of transcribing it, it's got to be pretty good.