Hi Empearor,
From what i've read, the Pure base is a low cost Silent base.
Low cost means no acoustic foam, less fan in bundle, acrylic instead of glass for the window.
They are approximatively the same size.
I've you seen the Corsair Carbide 270R? It's a really really good and cheaper case.
But keep in mind that your case is like a good PSU, you will keep it longer than a GPU for example and it's the global look of your build.