I try to consider these 5 different aspects (I personally don't think you'll ever find someone who does all 5 perfectly at once since you always lose the power of one aspect in favor of another.) 1: Pitch (Vocal range, Accuracy) 2: Emotional connection (Expression, Originality) 3: Tone (Resonance, Breath support) 4: Variety (Vocal registers, singing styles) 5: Presence (Theatrics, attitude)