I'm in the same boat and it's comical. I have an x-stiff in my hybrid (when I play a hybrid). I've played X-stiff shafts in my driver that seem less "stout" than stiff shafts from other manufacturers. It's all a feel game at this point in my head. At the end of the day, given my tempo, I too always go back to AD shafts. I was an AD DI guy for eons, but in the last 2-3 years switched to the AD IZ instead. Seems to just be a better upgrade than the AD DI (I swing the 6s by the way). The reason I go with the 6 is due to my low ball flight. If I grew up outside of the winds found in my home state, I would probably be gaming a 7.
Ed, I saw your post about the blue board and switching back to the white board. Funny thing is, when I saw you originally post about going to a blue board, my thought immediately was "no way he sticks with that from what I've seen on his driver/swing".