You can see these calendars in the images below along with a write up of the chocolate calendar from Griffin.
As of this week, both of the Kinnerton ones are now out, with the cheaper one found at BigW (so far), and the more expensive one found at Aldi (so far).
Cheaper one (Optimus and Bumblebee on the front) - $3 at BigW - 24 days/chocolates (40gm).
Glossy one (just Bumblebee on the front) - $4 at Aldi - 25 days/chocolates (90gm).
We've been having Kinnerton advent calendars in Australia since the first Movie in 2007, so the format hasn't really changed - a thin cardboard package with a plastic tray inside of 24-25 chocolates that you access by opening up doors/flaps for each day of December. (basically, you need to get this, or give this, before December 1st)
I think images printed inside the packaging (revealed when opening the flaps) is new though. I'm pretty sure previous ones were just blank cardboard inside.