Is it just that nvarchar supports multibyte characters? If that is the case, is there really any point, other than storage concerns, to using varchars
You're right. nvarchar stores Unicode data while varchar stores single-byte character data. Other than storage differences (nvarchar requires twice the storage space as varchar), which you already mentioned, the main reason for preferring nvarchar over varchar would be internationalization (i.e. storing strings in other languages).