My client wants a blog set up in EE. However, from an SEO standpoint he heard that having your blog on a subdomain is better. A) What is the validity to this request and B) Would I have to use MSM in order for this to be managed all from the same admin? Thanks for any recommendations!
A) What is the validity to this request
I don't think having a subdomain for blog is better for SEO. Rather than, I always prefer to have SEO friendly URLs for the blogs like yoursiteurl.com/title-of-your-blog which can easily achieved by Pages module.
B) Would I have to use MSM in order for this to be managed all from the same admin?
Yes, you have to use MSM for this to be managed all from the same admin. For the MSM you domains or subdomain will be hosted at same server. See more from here http://ellislab.com/expressionengine/user-guide/cp/sites/
I agree with the above answer. I've not read anything about a sub domain being more powerful.
I might suggest just setting up the URL structure domain.com/blog/title.
blog.domain.com/title - there is no real difference. I can't imagine the search engines ranking one over the other. If you are going to do a huge amount of blogging and article writing, then you may want to split this.
We do a fair bit f SEO, and not heard of this. I'd be interested to hearing what others have experienced.