Which of the 5 premade commander decks is the best?

Me and my friends are considering each buying a commander deck to try out EDH. I'm curious to know which deck, if any of them, is the best. If someone wouldn't mind giving a rundown of each deck's theme that would be awesome too. Also, how customizable are each of the decks. I'd like to be able to, as I gain more experience, improve and change the deck and make it more of my own.