There are many people how debating on that the blog on subfolder is good for SEO rather than place a blog on your subdomains. Mostly people are used subdomains for their blog because they are feeling comfortable to mange blog on separate place. On the other hand mostly people are using WordPress for blogging and if they are running an other app on their main site they couldn’t use mange blog on the main website so that’s why people prefer to use WordPress on subdomains of their websites.
There is different opinions in Subdomain and Subfolder
Mostly people think that it doesn’t matter if you choose subdomain or subfolder for placing your blog. But the reality is that people have experienced to switching their sites from subdomain to subfolder and they got so positive impact regarding to SEO point of view. When they switched their websites subdomain to subfolder they got high ranking in google and also increased the organic traffic up to 40% which is so good for a website.
Before you go for subfolder you should have keep in mind about your strategic objectives. But according to analysis if you want to high rank in google and get quickly organic traffic from google then you have to use subfolder for blogging. If you are using subdomain for your blog you have to switch your blog into subfolder.