The SPK's are kind of wierd at first cuz they have no foward lean, but the boot is stiff and the tongue is fat as fuck its super comfy and really solid. I like it.
Thats a good amount of stiffness. Kaos is 95 which iwould say is softer. But as far as park boots go Pros are definitely stiffer than most. Not Big mountain, charging boots though.
spk kaos is still an spk boot, same with the kreation and other models. he didnt mention "pro". they're still pretty soft boots, so in no way are they "stiff"