In the end you'll have more time and mental energy to apply to your other projects. You want it to be able to grow and change as you grow and change. Is reliable and located in a trusted spot. You can only guess what happens to your newsletter when it's hosted on a remote site, or when it's managed by scripts you don't understand. A solution you run locally solves this problem by putting you in control.
Handles subscribe and unsubscribe requests efficiently.
This will save you hours of time. Can schedule and automate the mailing of your newsletter. It simply can't. You need a management tool that can run things while you're gone. ROIbot Newsletter Server is a new tool that handles all of the above quite nicely.