If you have any hearing loss at all in both ears, you are better off buying the pair — even if your hearing loss in one ear is mild. Having one ear that hears much better than the other can stress the parts of your brain that process sound. Without similarly strong hearing in both ears, your brain will have to process the same sounds but at different volume and clarity, making for a less optimal overall experience. So unless your hearing in your other ear is perfect, we would advise buying the pair.