This is a very basic question, and one that doesn’t really warrant a long answer.
So, I’ll give you the short answer, then the long answer.
The long answer
Now here’s a more detailed answer. I’ll give you a rundown of what I personally like to use on my own WordPress blogs, and my reasons for them.
For every blog that I run, I use both posts and pages, and you should be doing the same. There are just some things that posts are better suited for, and some other things that pages are better suited for.
Let’s go through some examples.
When to use posts
For anything I want to include into my blogroll, I’ll create them as posts. They don’t need to be solely for “news” or “updates” kinds of content. You can use posts for long-form evergreen content. I use them for both.
For example, here’s an update style blog post I wrote a while back. It’s short and written as more of a journal entry than an actual information article.
And here’s a long-form evergreen piece of content I published. This post is over 4000 words long, and is a timeless piece on how to create content for new blogs.
Both of these are included in my blogroll. I like to mix in a combination of the two formats into my blogs.
When to use pages
I use pages for a few different things, but mainly it’s for content that I don’t want to include in my blogroll.
Usually, I’ll link to these important pages in my menu bar.
I also use pages for creating things like ultimate guides
The reason these are pages is that they’re not typical blog posts. They’re special. They’re way longer, and are custom designed. They’re also sometimes separated into multiple child pages.
For this reason, I choose not to include them in my blogroll.
Is there any affect to SEO?
No, not really.
A post or a page is simply an option in WordPress. To Google, it’s a webpage regardless if it’s a post or page.
Yes, sometimes, they’re formatted differently. But that’s something that’s determined by the developer of whatever WP theme you’re using.
Can you build a WordPress blog using just pages?
In fact, a lot of people do this. WordPress isn’t just for blogs. You can create static webpages using only pages.
The only challenge is that you would have to organize and format all the content links yourself since you wouldn’t have a pre-built blogroll.
Can you build a WordPress blog using just posts?
Well, you could, but it wouldn’t really make sense.
Not good organization at all.
If you’re looking for a right or wrong answer to this question, it doesn’t matter whether you use posts or pages.
Realistically, you should be using both. There really isn’t any reason not to. I like to organize my site by using posts for blogroll content and pages for everything else.
It’s a good system to use, and allows for a good user experience for your visitors.