When comparing FreeDNS vs Duck DNS, the Slant community recommends FreeDNS for most people. In the question“What are the best free dynamic DNS services? ” FreeDNS is ranked 1st while Duck DNS is ranked 2nd. The most important reason people chose FreeDNS is:
There are over 90,000 domains that can be used.
Question Ranking
Pros
Pro Huge list of domains to choose from
There are over 90,000 domains that can be used.
Pro Supports custom domain
Allows using own domain names.
Pro Includes url/port forwarding
Their built-in Web Forward system allows redirecting URLs (including to a different port).
Pro Detailed setup instructions for a wide variety of OSs
Duck DNS includes step by step instructions on how to set up their service on a wide variety of operating systems. There even are instruction on how to set it up on raspberry pi, mikrotik routers, tomatoUSB as well as multiple ways for Linux, Windows and OSX.
Pro DuckDNS sync app for Android
Cons
Con Using a custom domain gives everyone access to it
FreeDNS shares all custom domains used across all users.
Con Lacks advanced functionality
In an effort to focus on simplicity, Duck DNS lacks features such as custom domains, url or port forwarding and uses just 1 domain.
Con Difficult to use on some routers and NVRs
Routers and NVRs that give you set options (that don't include Duck DNS) won't work with Duck DNS. Apparently Duck DNS claims they support DynDNS or something of the sort, but the information it gives you, there's nowhere to plug it in in these boxes.