They all have to meet a certain standard (Snell or Ansi?) so as far as protection goes, they are all the same. If one manufacturer offered more protection than the standard, it would advertise it as exceeding the standard for helmet manufacturing.
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Il faut de l'audace, encore de l'audace, toujours de l'audace
1980 3Rensho-- 1975 Raleigh Sprite 3spd
1990s Raleigh M20 MTB--2007 Windsor Hour (track)
1988 Ducati 750 F1