Are you sure your motivation is correct, WRT pagerank?
I'd always thought that PR applies to your PAGES only. not domains. So, in your example, it's not that blog.twilio.com has a higher PR than www.twilio.com, it's that the blog.twilio.com INDEX page has a higher PR than the www INDEX page.
Thus, your PR isn't really affected by being on a subdomain, as the juice that flows through the system doesn't care about the sub/domain, only about the page and what points to it.
Comments
Are you sure your motivation is correct, WRT pagerank?
I'd always thought that PR applies to your PAGES only. not domains. So, in your example, it's not that blog.twilio.com has a higher PR than www.twilio.com, it's that the blog.twilio.com INDEX page has a higher PR than the www INDEX page.
Thus, your PR isn't really affected by being on a subdomain, as the juice that flows through the system doesn't care about the sub/domain, only about the page and what points to it.
Please correct me as needed.