Franz Schubert: Symphonies Nos. 2 & 6

Schuberts symphonies were designed for a big audience, but during his lifetime they were, at best, only performed in the semi-public rooms of the Seminary and those of the amateur orchestra. It was not until barely a month after his death that the first truly representative performance took place through the Society of Friends of Music (Gesellschaft der Musikfreunde) in Vienna. Leopold von Sonnleithner, a friend of Schuberts, had some input into the programming and suggested the sixth symphony for the occasion. The Great C major could not be considered owing to practical constraints, but why was it number 6 in particular that was chosen out of his early symphonies? Were the reasons purely mundane or was there a deeper rationale behind this decision? It would be good to know the answer, but today one can merely speculate.