The Chargers are def a stiff binding. They don't use the Atlas baseplate, they use the SL baseplate with is one of the stiffest I've ridden. They're not on the level of stiffness of the Ride El Heffe but pretty close. I wish I had gotten them over the SL's. The SL highback is just a little soft for being a strictly freeride binding. Still rips though.
The charger uses the atlas stage III base made with carbon injected.
The sl base material changed this current year to no carbon injected b/c of the charger to better diversified b/t the product lines. It is the same base model just no carbon.
2013 charger binding atlas base III = 2012 SL atlas base III ( both carbon injected)
2013 Atlas binding base III = 2013 SL atlas base III (no carbon injected)