Guild Hall Islands

What is the purpose of the Guild Hall Islands? What are the differences between the islands? Why would one guild choose one island while another guild chooses another island? What are advantages/disadvantages to consider regarding the islands for one's guild?

I understand the concept of Guild Halls but I am ignorant regarding the islands themselves.

from what I understand from reading another post, they are used as sort of GvG arenas.

Guild Halls are for looking cool, and playing GvG in.

The only difference is the layout, and they way they look. Pick one that suits your guilds style.

It's a lot less complicated than most folks think.

Is there any backstory to each of the islands? Legend, lore that type of thing?