This thread has given zero information so far, but it is the first thread that appears when you google 11x vs 12x Teebird.
I have had a 12x Teebird, and it was so useless that I pretty much would leave it out of the bag. The only reason I would carry it is because it was a stability somewhere between Wraith and Leopard. A LOT of discs are in that area, so it is nothing to brag about.
After getting a 11x Firebird and seeing how much better it flies than the 12x Firebirds that I have had, I figured I would order a 11x Teebird if just to find out.
Night and Day difference.
My 12x Teebird would flip over in a mild headwind, where the 11x did not, but it did not have a lot of slow stability. It really flew like a Roc.
Also, my 11x has glide that approaches my Rivers. Not quite as much, but very close.
The difference in these 2 discs are just incredible. They are the same weight, 170, and the 12x is a lot domier, where the 11x is flat, almost as flat as the 11x Firebird.
11x Teebird is an incredible disc. 12x Teebird, not so much...