They are 2 different themes. And they are from different developers.
You can look at them in the CrackBerry Store... read reviews and look at the ratings. There are differences in icons, and minor other differences. I think the iBerry one is also offered in more styles and choices
i think the backgrounds are diff. i actually have a different one too that has the iberry icons, but with the iphone phish in the background instead of just being black. oh and it's a zen.