Quality over quantity, 100%. I don't care if you write a dozen pieces a day, if none of them are worth hearing.
Maximize your output, for sure - but maximize it in the places that matter. If you're like me, it might take you three months to write something, but making it beautiful and powerful and meaningful it much more important than the speed in which it gets written.
That said, I don't want to negate @Ken320's perspective. Because he's also right. When I say quality over quantity, I'm ignoring the 2 months of rejected 8-measure sketches and garbage that looks like this: rj-process.pdf
Yes, write a lot ... write often. But don't be afraid to swiftly reject something and move on. Do keep everything you sweep aside. It'll be useful eventually. For me, the output is only about actual completed works - it might (like it does for me) take a LONG time to find something worth finishing, and it's these gems that are important to unearth.