One Page Site Vs. 4 Page Site

Is there any bonus to having more than one page other than to use the other pages as link "helpers" to other sites and the home page?

I would imagine "more content" on the sub pages would help the home page possibly...

Please educate me

I like to assume that Google has a smart enough algorithm that measures in some way or another how many pages on a given domain contribute towards a specific keyword.

The effect may be small but it could well be the difference between the first and second spot in some cases.

My formula is:

www.mainkeyword.com/index.php
www.mainkeyword.com/main-keyword-alt.php
www.mainkeyword.com/alternate-main-keyword.php
www.mainkeyword.com/main-keyword-too.php
www.mainkeyword.com/another-main-keyword.php

I'm trying to scoop up small niches that are my "mainkeyword". I've got at least 4 other pages which are related content to my main keyword, at least 300 words, most likely 600 words.

I'm not really trying to rank for the other keywords, but sometimes I underestimate the competition for my main keyword, that doesn't make the SERPs but my others do. I start promoting them instead.

Not using wordpress. I've got a template that is all set to go, I can have a site up faster than doing an install with WP.

the thicker ur site, the better in google.

More pages with good content and use of keywords is FAR better than 1 page. Content is one of THE driving factors for good seo.