The NTP ebuild says:
"The way ntp sets and maintains your system time has changed.
Now you can use /etc/init.d/ntp-client to set your time at
boot while you can use /etc/init.d/ntpd to maintain your time
while your machine runs"
That seems to indicate that ntpd and ntp-client should both be started. However, the wiki says:
"Make sure you are not running ntp-client"
I think the wiki is correct.
/etc/init.d/ntp-client doesn't keep anything running - it runs ntp-client, which sets the system time once and then exits, leaving the NTP ports free for ntpd (or a different NTP daemon) to take over.
Perhaps the wiki should be changed.
If I start ntp-client automatically at boot, it takes about 12 seconds and delays everything which starts after it such as shorewall and local.