It’s a close call as far as I am concerned as to which is my favorite of Mozart’s late symphonies:
Symphony No. 36 in C major, K. 425 (known as the Linz Symphony); or
Symphony No. 40 in G minor, K. 550.
I became acquainted with both at a very early age thanks to recordings my parents had. The “Linz’ Symphony was a favorite of my mother, Elinor Handy Smith.
I love the slow buildup in the opening of Symphony No. 36 (the “Linz”); it makes me think of someone tiptoeing up a flight of stairs.
According to a Wikipedia entry
The “Linz” Symphony was written by Mozart during a stopover in the Austrian town of Linz on his and his wife’s way back home to Vienna from Salzburg in late 1783. The entire symphony was written in four days to accommodate the local count’s announcement, upon hearing of the Mozarts’ arrival in Linz, of a concert. The autograph score of the symphony has not been preserved.
— Roger W. Smith