Different magnetically confined fusion reactor concepts, like the tokamak, the reversed-field pinch, the high beta stellarator and the linear theta pinch, are discussed by means of a few quantities prescribed by technical and physical requirements. These quantities are: the thermal reactor power, the wall power loading, the first-wall-to-plasma-radius ratio, the blanket thickness, the toroidal aspect ratio and the plasma beta. Pulsed operation was included by introducing a dimensionless time τ, the ratio of the burning time to the pulse cycle time. Other reactor and plasma parameters are derived from these quantities. Under certain assumptions, the systems are compared on a simplified basis in different respects including the energy balance, the question of Ohmic power losses when normal conducting magnets are used, cost structure and fast power supplies. Finally, the main features and advantages of each concept are summarized.