In small pools of up to 4-6 people, you get close focus from your instructor while getting the support, camaraderie and encouragement of working out with others regardless of your individual fitness level. Your instructor will ensure that the workout is appropriate for the entire pool but also adapted to suit your individual fitness needs.
Note: some personal trainers also oversee classes that are also available on SplitFit (at the discretion of the partner club). These may be larger than 4-6 people.