True, the number of applications will have the biggest effect (along with which apps those are) but for a newb who probably is looking for a default install, I would highly suggest you go with vector 3.2. I currently use it because I have a 1.7 gig hard drive that I use to serve ftp, and a default (complete) install is just 435 megs. I don't know about the SOHO version.
check it out at http://www.vectorlinux.com
btw, it is also very "lowmem friendly"