What's the advantage of using a hunt group vs. multiple registrations to the same extension?

IOW, when you have several phones that need to respond to the same incoming calls, you could either set them up on individual extensions and then place all those extensions in a hunt group, or you could simply register all those phones to the same single extension. What are the advantages and/or disadvantages of one method compared to the other.

I can think of a few differences, but how do others view these alternatives?

BTW, multiple registrations to the same account (i.e. extension) is part of standard SIP capability and should always be implemented. The Vigor will do it, although not very elegantly as it only displays the last registration and that changes as each phone updates its registration at the set intervals. It really should be able to display all phones registered.