If you add water to bring the proof to about 105 to all three I expect they would be very similar.People who say that they prefer the 122.6 over the 129 aren't saying that the 129 isn't up to snuff. I think most of them are saying that they find the 122.6 slightly more drinkable because it is smoother and "easier." It's like saying the 2007 WLW is better than the 2008. You're going to get a lot of disagreement, and no one is wrong- 07 is awesome for easy of consumption and 08 is awesome for the (perhaps) slightly more complex flavors but neither one is bad.
Anyone have firsthand experience?