There are times when a post should not be a post; instead it should be a page. What is the difference? A page is a daughter to a main home page and to a certain extent has a life of its own. More importantly, because it is a page and not a post, it can be linked to alongside other pages such as ‘About’ and ‘Contact’ – often in the header section of your front page.
Pages get treated differently to posts in most blog software platforms. In WordPress, you can constantly modify your pages and WordPress doesn’t react, unlike a post which gets pinged every time you make a change (unless you install plugins to prevent that).
A well written page can be a center piece for your blog. It could contain helpful information, a ‘how to’ piece or perhaps information such as a corporate or product history. Generally speaking, posts are fairly short at around 500 words. A page can be as long as you like, although there is a good argument to break a long piece into two or more sub pages.
The page content could be a collation of several posts, particularly if you have written a series. Rewrite the series into one long page and publish it separately. Link from the series posts to static page. As you update the page, you can write a short post advising every one of the changes. This brings this page back to everyone’s attention again.
From an SEO perspective, static pages make a lot of sense for information that could be of use to readers instead of simply using a post.
I would suggest that the question is not a simple choice between one or the other seen as an integral part of a website’s marketing and content generating efforts. A WordPress blog is perfect for creating fresh content and building up the number of pages on a website. It also gets syndicated via RSS and has great value in this also. But with a seamlessly integrated on-site blog, I really don’t see the difference between a post, which is in itself a page, and a page.