You'll feel like you've lost a lot of control of your board when you go from softer flex to stiff flex. Going from a 4 to a 6 is pretty significant. If you haven't tried them on and tried flexing your ankles and testing the motion with the stiffer boots, you ought to try them on in the store for awhile before you buy them. And put your soft boots on before you go try the stiff flex so you'll be able to tell the difference. Typically softer boots are more freestyle and park riding while stiffer flex boots are for all mountain and high speed riding. Good luck
Well, I found the Focus locally in a 1/2 size bigger, so it wasn't a perfect comparison. They were obviously stiffer and heel lift was slightly less even though the size was bigger and not molded to my foot. Some still say its a good all-mountain boot. Others classify it as a freeride boot. I'm still very new at snowboarding and probably won't be hitting speeds over 25mph for a while. I'm concentraing more on carving and speed control. Question now is, fit aside, will this be a poor choice of boot for me based on what I just mentioned?