I looked at Official Ticket Center, Park Savers, and
Undercover Tourist.
OTC had the best prices for what I wanted, but when it came time to submit my order, it just looped, with no error message. That, plus incomplete security caused me to give up. (Incomplete security means doing things like having insecure images on an otherwise secure web page. Because of the way browsers tell you about the page security, it's a bad idea to do this, even though it's technically not a security hole.)
PS doesn't seem to have physical tickets, so I gave up. Also, Touring Plans had a link to Park Savers that should have explained how to link a ticket voucher to
MDE, but it was a dead link. I can't tell if that's TP's or PS's fault.
So I gave up on both of them and went with
UT. Upgrading to include the water parks brought their price in line with the other two. The web site is much smoother than either of the other two, especially the checkout, and that means something for me.
Possible Tip (I think): Because of the convoluted pricing, a 5 day PH+WP ticket was $20 more than a 4 day PH+WP ticket. But from what I can tell, it will only cost me $10 to upgrade at the park - and I can wait to see if I want the extra day. Or am I missing something?