It doesn't seem to make much of a difference in the size. Their silicone Evolved, long vibes seem to come in the plastic dome while their rabbits seem to come in the tin. Some other vibes (like the Lavish) comes in the tin. It seems to be much more of a "from toy to toy" difference than in the size.
However, if you're really gunning for the tin, I highly recommend reading reviews over the toy before you purchase it. A lot of times, the reviewers will mention what packaging it comes in.
(I love the tins too; they rock.)