AJ, the simple answer: Spring King. As Chaz pointed out, I'm a BIG
I do feel pretty strongly, though, that, with very slight kneading modifications, you can get the same pizza out of 12.6% flours as you can 13.4%, so I'm a pretty big fan of almost every flour on my list. The one outlier would be Occident, at 12.2. Norma, along with other members, has done some amazing things with Occident, and Occident has an uncanny ability to show up in some communities where nothing else is available. At 12.2, I'm not as gung ho about recommending Occident, but I feel pretty strongly that it's better than All Trumps- it's easier, imo, to push a weaker flour to give you more gluten than it is to prevent an extremely strong flour from giving you too much.
I talked about this subject, in depth, quite recentlyhttp://www.pizzamaking.com/forum/index.php?topic=30887.msg308979#msg308979
While I do feel strongly that these flours can all make the same world class pie, if you had multiple options to choose from, this is the order I'd go with (from more preferred to less):
Progressive Baker Spring King 13.2
ADM Commander 13
Conagra Magnifico Special 13
GM* High Power 13
Progressive Baker Spring Hearth 13
Conagra Producer 13.4
GM* Best Baker's 12.9
GM* Full Strength 12.6
Conagra King Midas Special 12.6
GM* Superlative 12.6
GM* XXXX Patent 12.6
ADM Majestic 12.6
ADM Springup 12.6
Conagra Occident 12.2
Bay State Milling Perfect Diamond 12.5?
Bay State Milling Aristocrat
*General Mills or Pillsbury or Gold Medal (all the same company)
Disclaimer: In terms of what we know about these, I think there's still data to be collected, so this list will most likely change.
Also, I wrote the BSM rep and am awaiting numbers for Perfect Diamond and Aristocrat.
Edit: these are all the bromated versions. I do not recommend any of these flours in their unbromated versions. For those in the West who don't have access to bromated flour, right now, I'm leaning towards a Pendleton Power/Mondako blend.