Generally a custom laboratory mouthguard will be the best for your sporting needs. These can be purchased from online mouthguard stores and dentists.
Athletes participating in full contact sports where facial trauma and concussions are common such as football, boxing, MMA, hockey will benefit from a mouthguard which covers all the teeth in one arch including the front teeth and the molars. This mouthguard should be at least 3mm thick. A one piece two arch mouthguard can protect both dental arches and works well as long as there is a significant breathing space in the front of the mouthguard. Minimal contact sports still benefit from mouthguards but can be less bulky and allow athletes to speak better to their teammates.