Considering how old these recordings are, they sound tremendous. Considering who the performers are, they sound terrific. Considering what the repertoire is, well, there is only so much performers can do.
The 1949 Decca recording by Erich Kleiber leading the Orchestre de la Société des Concerts du Conservatoire in Tchaikovsky's Symphony No. 4 sounds rich, warm, and real. Kleiber's conducting, however, is unsympathetic at best, and brusque at worst, the Orchestre de la Société's playing is soft and sloppy, the piece is pathological neurosis and degenerative hysteria made music, and the combination of a brusque and sloppy performance with abominable music is hard to take even in real sound. The 1953 Decca recording by Erich Kleiber leading the Orchestre de la Société in Tchaikovsky's Symphony No. 6 sounds even richer, warmer, and more real. But Kleiber's conducting is even more antipathetic, the Orchestre de la Société's playing is even more torpid, and the piece is pathological morbidity and degenerative insanity made music and the combination is even harder to take.
One expects much more from Erich Kleiber and in repertoire from Beethoven through Berg, he delivers. One expects not much more from the Orchestre de la Société because, after all, they were a French orchestra that typically refused to play together because it would compromise each member's individuality. But except in performances by Mravinsky or Mengelberg or Stokowski or Furtwängler, one expects next to nothing from Tchaikovsky because, after all, he was one of the worst Russian composers of the nineteenth century.