The diference between cosmo line and stacker line, is the diferent coolings they are designed for.
Cosmos Cases, are a lot better with watercooling, since they have precut holes, extra top space for radiators and so on.
The stacker is mainly designed for crazy aircooling, you can easily mount 10 fans.
I like more the 38x series, because of the high quality aluminum, EATX form factor, and the overall design.