So you have content, but you are not sure you want to go with pages or posts. Well, it really is not that difficult. A lot of people put together a site completely in posts without few pages. Or they make a page and enable comments, depending if their theme has that coded into the page template.
Even you can customize individual pages, since WordPress 3.0, you can customize individual posts. You also have the ability to adjust your menu from your WordPress admin panel to whatever you like if you have the wp_nav_menu php call into the theme itself.
Posts are normally considered an area of your website that will be updated frequently, while pages are more considered to be static. The difference- while both pages and posts are included in a sitemap (if you have a sitemap plugin installed… and you should), only posts are included in your RSS feeds (RSS- really simple syndication.) With the RSS, you can feed it into social network aggregation tools that will publish your posts to your social network handles.
However, you have to ask yourself – do you want comments on a page you will rarely update? What type of content are you putting up and how much of it? Remember for those internet marketers who like to use landing pages, enabling comments on a squeeze page might not be ideal.
If you like to put up mass quantities of items, for example, pixel images where you have a lot of images, you may want to use a page. Or you could release a few at a time in posts.
This is really something you have to decide on how you want to organize your site. If you make a page, you will have to announce the page somehow, especially if you want to drive attention to it.
Navigation is a big part to most sites. It is often the source of a visitor’s problem if your site is confusing to go from one area to the next, and back again with ease. Both posts and pages allow you to implement elements like breadcrumb navigation (a navigation you put at the top that tells you the path from that page you are on, and gives you a way to go back to the home page), links for next and previous post, navigation with numeral navigation (instead of older or newer post links), WP 3.0+ navigation menus, subpage navigation (you can have whole sections as a parent page and then children pages related to that section) and more.
It boils down how you want to organize your site. In fact, your sites organization has pull on your SEO. If search engines see that you have sections of your site that are grouped, they will list those under you
I usually put posts for what I am going to talk about and pages for things I may not update a lot.
Here is a good example of what I was talking about:
How have you organized your site by using pages and posts in WordPress?