depends on what kinda design laa. if we're talking about architectural/interior designs, then i'd say PC would probably preferrable. not better, just preferrable.

as for desktop vs laptop, go for desktop. i find that two harddrives in a desktop is a safer alternative. u can always backup ur work, and if one got screwed, u'd still have another. i've seen too many of my students coming in during submission day on the verge of tears coz their laptops kong last minute.

as for style, ofcourse laptop is more savvy. so get both laa. ur REAL work is at home, but when u wanna look 'cool', bring ur laptop. careful with the GEEK vibe though.