I don't know much about specific models, but I did a lot of research before I bought my POC receptor+. It's a good helmet, but it's very heavy. Good for developing afterbang.
Anyway, most helmets are EPS which provides good protection through plastic (permanent) deformation. Once the foam deforms, it no longer absorbs nearly as much energy, and you gotta get a new one.
Some helmets are made with EPP (POC receptor+ and Bern hardhats to name a few). EPP protects you with elastic deformation, and is good for multiple impacts. The problem with Bern's hardhats is they're really thin. They're also not certified (receptor+ is certified and MUCH thicker than the Bern). This could be because it's so thin it didn't pass certification, or they didn't feel like paying the money for the cert. I got a receptor+ cuz i hit my head alot and don't wanna get a new helmet each time.
I've had a Bern baker hardhat, POC receptor+, and then some giro a few years ago that saved my ass when I crashed into a snowboarder (my bad...) and his edge hit my head. The hard plastic shell and foam (EPS) totally cracked but I walked away unscathed.
Also nick is totally right about rotational forces being the primary cause of concussions, and that conventional helmets don't dampen them at all. Unless your head is moving in a straight line, when it hits something your brain spins and the grey matter on the perimeter tears and you get a concussion.
Sorry if this is TMI but I wish someone told me this when I was buying helmets.