Detection limit improvement factors have been calculated to predict the improvement in detection limits when replacing a traditional 20% coaxial detector by either a 100% coaxial detector, a well-type detector or by equipping the detector with a Compton suppression shield. It is show that, when measuring sources on the end-cap of the detector, a system with a Compton suppression shield and a 100% detector have almost equal potentials. But when e.g. geometrical consideration larger source-to-end-cap distances are required with coaxial detectors, the well-type detector offers the best outlook for attaining better detection limits. The calculated predictions have been compared with experimental observations and the results agree well.