What did your helmet look like after your crash ?
My 6D Helmet busted the beak off during the crash, including breaking 2 of 3 plastic beak mounting screws and had lots of dirt scars all over it. When I hit the ground at 4th gear pinned 450 speed in the fastest section of the track, I know that my body did at least 4 or 5 complete out of control rolls before I ended up face down in the dirt. Felt my knee come out of it's normal range of motion during those rolls and my mind was concentrating on my knee. It swelled up huge immediately and required surgery to fix all of the damage from the crash. My head was fine.
Of course no helmet can protect you fully from injury, it depends on the crash and the way you hit the ground, and a million other factors that you are not in control of when you test your helmet and your head's limits in a crash. Who knows, I may have been fine with my previous Fox helmet with MIPS as well, but I made the choice to change to 6D for the scientific backed testing in protecting my brain. Why not? I want to keep my wits about me even though I'm destroying my knee more and more and the doctor said I'll be a knee replacement guy for sure. I have no ACL, PCL, or meniscus left in the knee, lots of arthritis starting, and plenty of cartilage damage in there, but he smoothed it out enough for me to feel well enough to sign up for Loretta's and race 2 motos before breaking my pelvis in the 3rd and final Moto which put me back in the hospital for 3 straight weeks and bigger problems than my knee. 3 straight weeks in hospitals, and 8 total weeks in a wheelchair, just back to walking some now. But back in PT and training for next year already, can't wait to ride in the spring.