Nearly all of them use a UK Mooncup for illustration purposes and what I've noticed is that Mooncups really POP open! There's one video in which I'm surprised it didn't break the glass when it did. Now that I've seen the difference, no wonder so many on this list love their Mooncups. They seem super easy. No struggling or repeated stirring.
EDIT: 8 June 08 -- Many thanks to sweetrush for the revised Mooncup capacities!
I have deleted my concerns regarding the erroneous numbers on this post and the size/capacity chart has been updated as well.