Pros: Easy to enter, Easy to switch modes, improved downhill performance, swappable
Cons: Heavy for a tech binding
The Onyx provides several things missing from the typical tech binding (read: Dynafit). First, they are easier to get in to. True, you do have to hold the toe pins open with a ski pole, but since the pins are closer together when open it is easier to align the pins with the inserts. Secondly, you do not have to exit the binding to switch modes, or figure out the secret Dynafit mojo move. Just lift the red lever at the back of the binding to lock the heel, or press it down to free the heel.
The factor that is less obvious is how G3's Onyx ups the ante with downhill control. Because the toe jaws are normally closed, it has a greater clamping force to hold you in AND it simply can not be made to accidentally pop open if you twist your foot far enough like classic tech bindings. In addition it gets extra support from the ski brake at the back so you aren't suspended between the toe pins and the spring steel heel bars. And finally, it has a low ramp angle for a more neutral stance.
All this creates a new level of downhill performance and confidence unheard of for a tech binding. There are other nice features as well, like the ability to easily swap the binding between multiple skis thanks to a plate mounting system.
The cost of all this extra convenience and confidence? Weight, but still less than four pounds per pair - which is a huge improvement compared to six pound plate bindings like the Duke or Guardian.
More details at earnyourturns.com.