IMHO, it depends on what you want.
If you're using both protocols (v4 and v6) to offer the same service (eg IMAP/S, or HTTP, or whatever), and you want clients to be protocol-transparent - that is to say, if you want v6-enabled clients to use v6, and others to use v4, and no-one to care about which they're using - then use the same hostname in each record.
If you want people to be able to select protocol by hostname, use different hostnames for A and AAAA records.
So, for my webserver, where I want clients to be protocol-agnostic, I use the same hostname:
www.teaparty.net. 3600 IN A 126.96.36.199
www.teaparty.net. 3600 IN AAAA 2a01:8000:0:4::1:1
For my ntp pool server, where I decided I'd like people to be able to select the protocol, I used different ones:
ntp.teaparty.net. 3600 IN A 188.8.131.52
ntp6.teaparty.net. 3600 IN AAAA 2a01:8000:0:4::123:123
Work out what client behaviour you wish to encourage, and make policy accordingly.