(╯°□°)╯︵ ┻━┻
Next time, please WAIT until the FAQ is posted before you post. We know you're excited to comment, but give us a bit of time to set things up, OK? 
To follow up on what Root said, cards from List B are generally niche cards (all but Deflagration and Immolation were buffed in some way, probably because of their lower usage stats) that you don't want to run 6 copies of one, so there's more cards to choose from.
Sorry, didn't realize a FAQ was coming :p And thanks for clearing up the reasoning behind the two lists; they just seemed like random cards to me. I know deflag, immo, cat, and flooding have changed since I started playing, but the rest must have either been changed before March or else I didn't notice, and all the cards in list A were in-game when I started.
Other than to use Sanc or Warden, I still think picking list B will yield stronger decks, but we'll see...

I can't remember nova or immolation being in a tourney for quite awhile (other than last week's upped one for nova) so this should be interesting.