Here is an interesting story regarding the supposed conflict between quantity and quality.
In their book Art and Fear, David Bayles and Ted Orland describe an experiment conducted by a pottery instructor. This instructor divided students into two groups - a "quantity" group and a "quality" group. The first group would be graded according to the sheer amount of pots they produced over the course of the semester, without regard to quality. The second group would be required to produce one single pot, and would be graded according to its quality.
At the end of the semester - lo and behold! - the pots of the highest quality were produced by the quantity group.
Is it the same for all areas of creative endeavor, do you think? Is it the same for writing?