Part one of an occasional series about SmoothWall Express (SWE).
The SmoothWall Express source tree contains two NTP daemons - both ntpd and OpenNTPD. SWE uses the openntpd daemon, but installs the ntpdate and ntpq utilities from the ntpd package.
This is justified because openntpd is apparently more lightweight than ntpd. But note that ntpq does not work with openntpd.
On my machine, the saving in memory is not massive. As observed in the thread, openntpd needs to run two processes (with one running as root), while ntpd can use Linux capabilities. From a cursory look at the Debian bug tracker, ntp has more bugs, but they don't seem as important as openntpd's. I suspect ntp gets more testing. The latest portable release of openntpd was in May 2006.
If I ruled the world, I'd choose ntpd over openntpd.