OK, and compared to what? "Less" is a comparison, but you didn't specify what you're comparing Debian to.
Out-of-the-box RAM usage is a pretty specious metric because you're not installing Debian (or any other OS) just to have sit there in its out-of-the-box condition. Do you think a Debian server running Apache with 1000 vhosts will use less RAM than a RHEL server running nginx with 10 vhosts?