Here are results of some tests made with help of clknetsim. Compared is ntp-4.2.6p3 in various settings with chrony-1.26. The scripts used to generate the results are here.
Some visualizations of clocks controlled by ntp and chrony are here..
Here are older results with ntp-4.2.6p2 and chrony-20100614git (when version is not specified), chrony-1.24 and chrony-20100817git.