Action Mailer ... and two styles to choose from

It appears there are two ways to create mail with Action Mailer:

I use this way, I noticed exception_notification does as well:

def confirm(order)
  subject "Some subject"
  recipients order.email
  from @@from
  body :order => order
end

AWDwR P1.00 printing, November 22, 2006 uses this way:

def confirm(order)
  @subject = "Pragmatic Store Order Confirmation"
  @recipients = order.email
  @from = 'orders@pragprog.com'
  @sent_on = Time.now
  @body["order"] = order
end

The later has been around as long as I can remember, while I _thought_
the former was the "newer" way. It seems much cleaner, but it would be
nice to clear up the confusion on where this all stands. Which should
be used going forward?

Joe