any one who thinks that the met would not protect should know that all helmets are only tested to 17.5mph in a crash so no matter what helmet you have it has to protect you and they all will break at over 17.5mphI'm sorry to say this, but that is b*lls
the CE EN1078 standard is the minimum safety specification for helmets sold into the European Union, and your information is based on that specification

however, many DH full-face helmets substantially surpass this standard
specifically the Giro Remedy which is one of the toughest MTB full-face helmets on the market, and one of only a handful to meet ASTM F 1952 - the Remedy looks "oversized" and the reason for this is the thicker shell and thicker liner (foam) to meet the new standard which demands increased protection for the higher speeds and impacts common to DH racing
the ACU Gold standard to which MX helmets are rated, is another step-up from the MTB helmet in terms of impact energy absorption; this is why MX helmets are substantially larger than MTB helmets and often heavier, unless using multiple composites (which means a helmet typically costing £175+)
have a look at this:
Standards: Lab test protocols designed to prove that a helmet can manage impacts and has the necessary coverage and strap strength to perform well. Designers typically design to meet a standard but not exceed it by much. Bicycle helmets typically are certified to:
* CPSC: the legally-required standard for any bicycle helmet sold in the US.
* ASTM F 1952: downhill mountain bike racing standard requiring more coverage and more impact protection than CPSC.
* ASTM F 1492: ASTM skateboard standard requiring four hits in one spot and more coverage but less severe impact protection than CPSC.
* ASTM F 2032: BMX standard requiring more coverage than CPSC.
* EN 1078: European bicycle helmet standard requiring less impact protection than CPSC.
* DOT: US Dept. of Transportation motorcycle helmet standard requiring much more impact protection and coverage than CPSC, but sometimes met by BMX helmets.
* Snell M-2005: motorcycle helmet standard requiring much more impact protection than any other in this list, and the only one that requires that chinbars be able to manage impacts.
the ACU Gold is similar to the Snel M-2005 for all intents and purposes