If I understand your question correctly, yes, there is a slight difference in SEO based on whether you create a Page or a Post.
It has to do with how Google interprets the content. If you create a Post, it will automatically appear in things like Categories and Date Archives, and themes often display the updated date. These signal to Google that this is a timely article - best suited to queries that are time-dependent. For example, if you are talking about an annual event and writing details that are specific to the current year, a Post is a good way to go because it signals this is specific to the current month/year.
Similarly, if you are talking about that annual event but want to keep a single page which you update every year, a Page would be the way to go because it is seen as more static content. You could still add Schema event markup (in this example) to signal to Google that there is timely content, but over time you would build up more links to this one URL than you would to a Post.
Finally, there may be differences depending on what kind of theme you use. Many themes use an
<article> tag around Posts but not around Pages. So the actual HTML that is rendered may vary somewhat and could be a little better optimized in either a Page or a Post, but this varies so much by theme you'd have to dig around and determine this for the theme you are using.
Overall there are not many differences, so as in almost all SEO questions, do what makes sense for your human visitors and the spiders will fare better as well.