Blog is about personal experience, if you had a blog for your Website, you can share your thought on your personal experiences about your niche related products or services. Article is what, you provide some information, facts, knowledge.
Content always matters a lot for both blog & articles, if you write through your own, not to worry about duplicate contents, it must be unique always however you can check for grammatical errors through online tools or Ms-Word and then post on your blog or article directories.
The difference between a blog post and an article is the content, its structure and its purpose.
If you notice, most of the blog posts are opinionated. So, they, more or less, are based on bloggers' opinions, ideas and thoughts about anything they experience or are experiencing. And they share it via their own blogs. The posts can either be short, long, or just a snippet with their thoughts on it.
An article, on the other hand, follows a certain format or structure. The sole purpose is to convey information based on facts or opinions or a mixture of both. Unlike a blog post, articles can be published to other sites or media.