I use both actualy..
laptop is handy for when I'm not home.
in the train here we have free wireless acces..
*so lately I love to take the train. (sniffing everybody with cain&able)
Last week I learned my girlfriend how to use cain to dns-spoof everybody on the train that where logged in. ;-) so when a passenger try to get to google or facebook
they ended up at lemonparty.com
at home the laptop is used for scanning and bruteforcing.
a sidekick
and for security, do much with tor or ip spoofing and vpn ofcourse.
al my important juicy stuff are located on 1 external drive.