... and guess which has fewer features.

You can write a tiny daemon which just sends and receives NTP network packets, with just a few lines of code. If you're satisfied with the resulting accuracy of your system time then that's fine. This is called SNTP.

It's not just a "Linux client". The code base can be used on a wide variety of operating systems, including Linux, *BSD, Solaris, a few other *IX-like systems, and Windows. It also includes lots of code which allows using it as a primary time server which gets the accurate reference time from a directly connected GPS receivers, or similar.

Why do you think ntpd provides only seconds or minutes accuracy? This is certainly not true. In a normal local LAN with Linux or *BSD machines you can easily yield sub-millisecond accuracy between real NTP nodes. If you run Windows, though, the accuracy which can be achieved is much worse, which is due to the limited timekeeping capabilities of the windows OS. The trick is not in the format of the network packets but how good an NTP *client* evaluates the packets received back from a server, does statistics to reduce network jitter and outliers, adjusts the local system time, and compensates the clock drift of the local machine which varies with ambient temperature, system load, etc.