Most firmware in older VOIP phones can not handle the new IPV6 scheme.
So, to prevent yourself some headaches, tell your home router to use IPV4 addresses on your home/office LAN.
Some newer VOIP phones might be able to handle IPV6. But if you aren't sure if your endpoint can handle it, then just use IPV4 to be sure.
If your phone can't get a LAN IP address on your home/office network, then you wont ever be able to use automated provisioning or even use your endpoint if you manually provision it.