For what specific reason would a person need stiff bindings?
You have a $1500 board and are not sure why you would or would not want stiff bindings?
That's like saying I just bought a Porsche but I'm not sure if I want to put summer or winter tires on it...
Just because the Mystery has a fast base, doesn't mean you can make it go fast.
Reminds me of a kid I met on the slopes when I was an instructor. He had a Burton Method with C60 bindings and Burton SL boots... easily over $2000... and he fucking hated it. I couldn't help but get a lil chuckle out of it.
Stiff bindings are for carving and high response at high speeds. Choosing a stiff binding due to it's weight is the wrong decision to make. Choose a stiff binding, like the Diode, if you have a stiff board and want instant response at the cost of cushioning and flex.
The mystery is a 5/10 in flex but directional, so not a true freestyle board. I would say the Cartels would be great, but if you have to blow some cash the Genesis would be a better bet than the Diodes.