A Core is not much bigger than a Kisado. In fact, the Kisado is longer. Plus, a Core doesn't stick a mile out of your system just waiting for someone to snap it in half. Seriously, converters are so ghetto. Its like buying a bra for the front end of your Chevy Cavalier. Lame ass.
I'm fully aware that not everyone wants to just hoard craploads of systems, but really you only need one system; any Duo, if it is modded. The mod usually costs less than a converter, and would certainly be less "clutter". Plus, it would work better than most converters (ie: no Arcade Card problems)...and you can close the HuCard door. Awesome!