for IPv6 there are two types of address format. AAAA? and A6?.

AAAA? is the simple one, it works just like an A record in IPv4, but with more bits.

A6? supports fragments of IPv6 addresses, so you can have "example.com" has the fragment "2002:c000:0201", "engineering.example.com" can have the "example.com fragment" + ":0001", and "foo.engineering.example.com" can be "the engineering prefix" + ":0000:0000:0000:0001". This means that when example.com renumbers, they change one DNS record (example.com) and "pewf!" all of their machines have been renumbered.

Now, people complain that A6? is too complicated, and prone to problems (what is the TTL on the response if the fragments all have different lifetimes?, whats the status of it if some of them (but not all of them) are signed with DNSSEC? What protection is there against DoS?).

The A6? people say that it's necessary for networks that regularly change IP address (eg: networks that use a dynamic 6to4 address).

A6? in general is the newer standard, and AAAA? is the older standard, however, there doesn't appear to be much momentum for A6? support.