We are just adding a subscription for those that want blog updates. We have been using exclusive lists that we have managed for a few years, and we only send specific content based on those lists. We have just recently added the option to subscribe specifically to blog updates.
I think the key is to have differentiation. If you have an exclusive list, that is pretty much just you picking the blog entries you want to blast out, then there isn't much differentiation and I think you'll confuse your readers. If you have an exclusive newsletter about investing in real estate, or something like that, then the reader can easily differentiate where they want to sign up, and may sign up for both because they are different.
Here is what we do. Not sure if it will help.
We have specifically placed the "subscribe to blog updates" option on top of the blog (and soon to be on the blog posts as well). We have also added a subscribe to blog check box on the comments section (We are using a mailchimp plugin for this, but there is one for Aweber I think). Then we just have this set up to email every week the latest posts. They will only see this sign up if they are looking at the blog home page or on a specific post. If they aren't they won't.
Then we have our exclusive sign ups. We are constantly pushing to specific pages to sign up for exclusive, specific topics they might be interested in, and have option to view those pages by clicking icons in the sidebar. These are on all pages.
Not sure if that helps, or even makes sense. Again, I think a lot of it depends on what your exclusive content is. If it's exclusive content on a certain subject, you will be linking to that content throughout posts, possibly put it in the sidebar, etc, and it won't matter if you offer the blog updates on the same page because they are completely separate options, and the viewer will sign up for whichever they are interested in.