DC just have a bad rep. Period. To progress does not refer to the boots, it refers to level of riding/skill. Intermediate rider doesn't really specify what type of rider you are. Park, all mountain? back country? jibber?
Stiff flex boots - for serious riders who want speed
Mid flex- all mountain ppl
Soft flex- park and jibbers
But the best way is to go out to your local shop and try out the boots. Find one that fits your style of riding, and find one that is COMFORTABLE. Mind you, comfortable boots might cost a higher price.