I think you're wrong about Beethoven - he took the legacy of Mozart in a surprising direction. He was the first to use trombones in a symphony, and basically invented the idea of using a choir in a symphony. He also played around with key relationships and programmatic music much more than Mozart.
Mozart was the better composer, I think, but less innovative - his genius lay in stretching the conventions of his day just short of breaking point. Beethoven broke the elastic.
I've not done academic research either to back up these contentions.