Simplenews vs civiMail
It's technically possible to use either CiviMail or Simplenews, but the real questions in my opinion, are:


What else are you using CiviCRM for?  Donations, memberships, etc?
If you're using Civi for lots of things, wouldn't it be nice to run reports on Donations vs. Mailings and keep your data in a single place: CiviCRM?