Get the race 3.10 bindings, they are cheaper and you would be a little above the middle of din setting 3 to 10 at 6 . Only one thing, if i remember right the 4-12's mite have more vario settings. The 3.10's have 3 setting and i think the 4.12's have 5 settings. Vario setting is in which the binding moves forward or backward to give you differnt effects on the ski. Example move bindings to forward setting and ski becomes quicker to turn, and set it back and it turns slower and gives you bigger sweeping tunr for high speed. One other thing you mite consider is that the 3.10 have a upward toe setting of hard and soft were i beleive the 4.12's have a setting of hard and locked. I just got the 3.10's on my 9.20's this years models.
This years Atomic bindings they have done away with the "race-race" and just have "race" bindings for less confusion.