There is a debate whether to include your blog within your website or to set up with a separate URL. Here is an article that makes a strong case for including your blog within your website. Most of the argument in favor is based on the fact that with a typical small business website, you have ten to twenty pages of static content – much of it unchanged over time. With a blog you can double that content within a few weeks and it is continually fresh content as well.
To be fair, the article doesn’t address whether it makes more sense to have a separate blog URL or not but it does suggest that the critical issue in terms of Google visibility, is having a blog for your business.