Does exchange push email use more or less battery?

[kirstein]

I would like an explanation of how the exchange implementation works on my TP2. I've seen some posts saying that exchange push kills battery, and other posts that say that push uses the normal notification channel on the phone which is always alive anyway, so it doesn't use any extra power until the email is delivered. Is there any definitive explanation as to how this works, and would it benefit battery life to switch to an exchange server rather than checking for new messages every 30 minutes.

Thanks