Here is the final comparison to help you decide.
CS-51 is only for the ID-51 series. It does not work with the ID-31, ID-52, or mobile rigs.
Before diving into the software itself, let’s address the "why." The ID-51 has a beautiful interface, but its menu system is deep. D-STAR programming requires you to input not just a repeater’s frequency, but also:
: A free, open-source tool that supports the ID-51 for basic memory channel programming. Connection Methods Programming can be performed through two primary methods: