It is widely known that for Google, Content Is King. In short, the more website you have, the better you are likely to rank.
The crudest manifestation of this is the more pages to the site, the higher it is likely to rank.
But not all content is equal.
Especially in their latest changes, Google has put more emphasis on the QUALITY of the content. Google isn’t hiding this fact either, Matt Cutts has said so in no uncertain words.
One aspect of this: Google has become more reluctant to index a page just because it is there. Instead, it is picking and choosing and may index only a fraction of your pages.
It has become clear that one of the major clues Google is using to determine this is the STRUCTURE of your website. So, for example, it is much less likely to index all of a blog.
This is something to pay attention to. I know of no hard-and-fast rules and it is certainly going to vary from site to site. So look at which pages Google is and isn’t indexing on your site, and experiment.