From an SEO perspective there are essentially two types of sites. Sites that change (dynamic sites) and sites that do not (static HTML pages).
With each type of site a unique optimization strategy is required. As an aspect of search engine optimization (streamlining your pages for high rankings) content development is often underestimated as a means to increase your web site positioning and return on investment.
Just like trying to compete with Wikipedia with a five page website, no matter how compelling those 5 pages are, there is a limit to their reach and range from the standpoint of content, popularity and links. Whereas a site with more pages if structured properly has a distinct advantage if leveraged properly.
Aside from the preference of your content strategy, two prominent search engine ranking factors are responsible for achieving a higher search engine position (1) relevant content and (2) link popularity.
Depending on your target audience, the keywords you intend to draw traffic from and the competition the more balanced your offering to visitors and search engines (starting from your value proposition and content relevance) your position is algorithmically deciphered and assigned using a wide array of ranking criteria.
Dynamic sites have a distinct advantage (for now) which is the ability to zero in on specific industry trends through creating unique content using the trend or relative keywords in a new post or series of pages. On the contrary, static sites (that remain unchanged for long periods) are usually from the old school of SEO. What is that you ask? Basic steps such as creating a page, making sure it is linked properly to other pertinent pages, strong on-page SEO (optimized links, titles and meta tags) and then augmented by a few hundred or possibly thousands of links.
This is still a very effective model for acquiring and maintaining a high ranking position, the value in the static site is, unless you link to it or link from it the stability of the page is not fluctuating and provide a solid base for high ranking search phrases. It helps to have the content you wish to rank for on the page, but it is not necessary as you can use off-page link building to increase the scope of the keywords your site appears for in search engines.
The other method is through using a content management system or database driven programming platform such as Drupal, .ASP, .PHP, ColdFusion, Ajax to hasten the internal linking process and organize your content based on categories or tags. There is a distinct advantage if configured properly and search engines are known to have an affinity with fresh content.
For example, a company intent on making an impact in an industry teething with competition can add one underlying element to their marketing plan to increase their user engagement and conversion – 5 posts per week or 3 articles per week to reinforce strategic keywords on other pages. The benefits of adding content over time become apparent after the pages begin to age and the website takes on the characteristic of a resource for topical information in your industry. This is known as developing website authority and is an extremely powerful tactic for procuring highly competitive terms (once again, consider a behemoth like Wikipedia for example that virtually ranks for every topic it consumes). Why, because of relevance, link popularity and traffic (the true Trifecta of a top 5 search engine position).
When this occurs a migratory step if the content is internally linked properly using traffic bearing keywords in links to connect the most relevant content to supporting materials or the next logical themed progression such as linking information on pistons to camshafts, etc. The second component aside from the internal links is feeding the pages enough quality inbound links to provide buoyancy in search engines.
There is a different threshold for each page, depending on the competitiveness of the keywords, some pages can gain national exposure with just a few links from the right places yet others require thousands of links over time to ensure a sustainable time released link velocity to defend the position acquired or move up until it hits the #1 spot for the respective related phrases.
This is not to say that smaller sites with aged links do not fare as well, but why settle for less if you can have every page with content acting as one gigantic reference where any combination of the words on the page can become keywords when paired with the appropriate search modifiers.
Less may be more in some instances, but probability favors content as it is simply a ratio of keywords to search volume augmented by link popularity and traffic that ultimately decide.