Hello, We currently have a business blog and it is blog.mywebsite.com. All my competitors have their blog as xxx.com/blog. Which one is the best practise.
That's more of a personal decision. However, you could have both - just make yoursite.com/blog redirect to the subdomain.
There's no significant difference in having blog as your sub domain or as internal page. Prior google was considering sub domains as separate websites and links from that treat as external links. But google changed that in 2011 itself..