The public IPv4 that resolves will almost certainly be NAT'd so attempting to connect to the router on that IP is folly. We will have hundreds of routers so I do not want to have to add a different port forward for each one.
AFAIK, you cannot force a browser to use IPv6 so what router we connect to when using glddns.com is decided by the Internet gods.
Obviously IPv4 ddns will be useful in many scenarios but in our case IPv6-only would be fantastic.