While the concerto is frequently compared to the Jupiter Symphony, Girdlestone considers its closest parallel to be the String Quintet in C, K. 515. The expansive first movement is one of Mozart's most symphonic concerto movements. This movement subtly slips in and out of the minor several times. One of the secondary themes of the concerto's first movement is a march that often reminds people of the then unwritten Marseillaise. Beethoven references this concerto in his own Fourth Piano Concerto. In addition, the famous motif in the first movement of Beethoven's Fifth Symphony resembles one found in this concerto. Also, Mozart's 25th and Beethoven's 5th concerti have a strong march-like theme in the first movement that is first played in minor and then soon appears gloriously in major. The tranquil second movement is in sonata form, but lacks a development section. It extensively uses the winds. The third movement is a sonata-rondo that opens with a gavotte theme from Mozart's opera Idomeneo. Girdlestone considers this movement to be very serious-minded. Like the first movement, it touches upon the minor; however, it ends confidently and triumphantly.
K. 503 has long been neglected in favor of Mozart's more "brilliant" concertos, such as K. 467. Though Mozart performed it on several occasions, it was not performed again in Vienna until after his death, and it only gained acceptance in the standard repertoire in the later part of the twentieth century. However, it is now regarded as one of Mozart's greatest works. Mozart's pupil Johann Nepomuk Hummel valued it, as can be seen in the influence it had on Hummel's own Piano Concerto in C, Op. 36.