The two major differences between DHCPv4 and DHCPv6 are the following:
The administrative model
DHCPv4 – The administrator enables DHCP for each interface. Administration is on a per-logical interface basis.
DHCPv6 – Explicit configuration is not necessary. This protocol is enabled on a given physical interface.
Protocol details
DHCPv4 – The DHCP server supplies the subnet mask for each address. A hostname option sets the system-wide host name.
DHCPv6 – The subnet mask is supplied by Router Advertisements, not the DHCPv6 server. There is no DHCPv6 hostname option.