I did a little checking (looked at the website and manuals). There are a few differences between the two (it simply does not make sense to me that one company would have two lines of filters that only look different, this strikes me as impracticale to maintain two products with some very different parts, even though others may be shared).
For one thing, I think the Emporers have larger media containers and filters than the Penguins (I am guessing here, though Marineland claims "45% more mechanical filter area", though they do not say compared to what). Marineland also claims "much as twice the filter cartridge capacity" as otehr filters "in it's class".
I am fairly sure the Emporer BioWheels are larger, also allowing for more area for bacteria to colonize. If your tank is slightly overstocked, or larger this is going to be better than smaller assembly. Marineland calls the BioWheels for Emperor filters "extra large".
Marineland says Emporers have two pumps, but make no mention of this for Penguins.
I was wrong about the media baskets, but I think there is more to these two filter types than mere looks and aestethics. The Emporers seem to be larger than the Penguins (as in nature, Emporer penguins are the largest of all species of penguin). There are also design elements that are different, such as the Emporers cover, that opens seperately over the BioWheel assembly and the media compartments.
None of these difference may be astounding, I admit, but I think it would be a simplification to just say the differences are simply in appearance.
\Dan