Quality of the content and the writing is much more important than quantity of articles. It is preferable to spend a lot of time researching facts for your article and then writing it to the best of your ability before you publish it than to dash off numerous poorly-written articles that few will bother to read. In fact, poorly-written hubs (or posts on other websites) pull down the overall quality of the site.
Also, if you want Google and other search engines to find your articles and rank them highly where they will gain traffic, you should write about topics in which a lot of people are interested and which do not already inundate the Internet. Keywords will help people find your articles (though you should not stuff your writing with keywords--in this instance, 'more' is definitely not 'better'). The better an article is written--grammatically, with an interesting style and great, non-hackneyed content--the more likely it will generate a lot of traffic.
The goal is to write so that people enjoy reading your articles and believe their content is credible. That is what leads to earnings. Yes, it's work, but anything worthwhile (even things we enjoy doing) includes work.