Oh, and one other thing I forgot to mention.

Because most of these devices are tethered to your helmet. They require your helmet to be modified in order to be installed. This is pretty questionable, some people raise concerns that drilling a hole in your helmet invalidates any safety certification it may have. Many helmets are now available with HANS posts from the factory. I have not seen any helmets with factory attachments for any other H&N device.
This is another advantage for the Leatt, since it does not attach to your helmet in this way, it requires no helmet modification.