Both of them are great and you can’t really go wrong with either but they do have their difference. For example, while both Cardo and Sena have their mesh technologies for connectivity, the Sena, communication is possible for an extra 0.2 mile over the mile Cardo provides. All the popular Cardo devices are waterproof to the extent that they can be submerged into water. Sena has not advertised their devices as waterproof but water-resistant, meaning a little rain won't affect them, but falling into a puddle probably isn’t the best idea. Lastly, Sena focuses on adding more and more features to their headsets, increasing functionality, while Cardo focuses on making their devices more practical and more manageable to control. It comes down to which features you prefer.