That's interesting... and now we know who made the posters for the convention.
I didn't think that Hasbro Australia would have an entirely exclusive poster of just 1000 units, but comparing the two, the artist (whom I can't see noted anywhere, or a signature - maybe the regular version has it noted) has fixed up the colouring of Bumblebee and Megatron, made Optimus look more vibrant, and removed the colouring on Starscream's head. And the really obvious difference (which I can't understand why), is the removal of Shockwave at the back.
The Convention version also has bannering that makes it look more like a comic cover.