prototype561

Hey guys i know this might be a dumb question but what are the diffences between the nightshade and the Z? What does each sub excel at? I hear alot of people saying very good things about the nightshades but not much info is floating around about the Z. I see that both are rated at 1500wrms(im sure they take way more), is one a SQ sub and the other SPL or a combination of both. Any help would be appreciated, thanks