Don't these two go hand in hand? The better you get at your craft, the faster you'll become. Unless you're constantly creating things you're not used to.
Personally I prefer quality because I just like the process of it, learning new techniques, studying perspective and life, messing with composition and panel layouts. It's fun. I've also gotten faster over the years because I've gotten better at working with those things. It used to take a week or more to draw a page without work taking up my time, now it takes about 3-4 days.