Heather,
Why not do both - blog AND have a newsletter? Not everyone who reads your blog will subscribe to your newsletter and vice versa. By doing both, you'll capture the most traffic and potential for return visitors.
The other comment I have (or rather a suggestion) is to think outside of the box and not limit yourself to serving the needs of job seekers. Think of what's next - how about helping those who have found jobs improve their communication skills, for example? Think along those lines and you can further segment your mailing list into sublists that are tightly targeted. You'll find that the response rate will be higher for such lists.
I wish you the best in your endeavours.
Hock