A neuromodulation system for use with a patient, comprising: a plurality of electrical terminals configured to be respectively coupled to a plurality of electrode sets; modulation output circuitry configured to independently deliver super-threshold anodic electrical energy and super-threshold cathodic electrical energy from each of the electrode sets via the electrical terminals to the patient, and to deliver sub-threshold electrical energy from an effective one of the electrode sets via the electrical terminals to the patient, the sub-threshold electrical energy being below a patient perception threshold and the super-threshold electrical energy being at or above the patient-perception threshold, the patient perception threshold being a boundary below which a patient does not sense delivery of the electrical energy and at or above which the patient does sense delivery of the electrical energy; memory configured to store an anodic perception threshold of the super-threshold anodic electrical energy respectively delivered from each of the electrode sets to the patient, and store a cathodic perception threshold of the super-threshold cathodic electrical energy respectively delivered from each of the electrode sets to the patient; and characterized in that the system further comprises a control circuitry configured to compute a ratio between the anodic perception threshold and the cathodic perception threshold for each of the electrode sets, and select one of the electrode sets as the effective electrode set from which the modulation output circuitry delivers the sub-threshold electrical energy to the patient based on the computed ratios. a plurality of electrical terminals configured to be respectively coupled to a plurality of electrode sets; modulation output circuitry configured to independently deliver super-threshold anodic electrical energy and super-threshold cathodic electrical energy from each of the electrode sets via the electrical terminals to the patient, and to deliver sub-threshold electrical energy from an effective one of the electrode sets via the electrical terminals to the patient, the sub-threshold electrical energy being below a patient perception threshold and the super-threshold electrical energy being at or above the patient-perception threshold, the patient perception threshold being a boundary below which a patient does not sense delivery of the electrical energy and at or above which the patient does sense delivery of the electrical energy; memory configured to store an anodic perception threshold of the super-threshold anodic electrical energy respectively delivered from each of the electrode sets to the patient, and store a cathodic perception threshold of the super-threshold cathodic electrical energy respectively delivered from each of the electrode sets to the patient; and characterized in that the system further comprises a control circuitry configured to compute a ratio between the anodic perception threshold and the cathodic perception threshold for each of the electrode sets, and select one of the electrode sets as the effective electrode set from which the modulation output circuitry delivers the sub-threshold electrical energy to the patient based on the computed ratios.