What is the difference between stock tickers UN and UL?

Unilever is a dual-listing, Anglo-Dutch company. The company, therefore, has two listed stocks. UN is for the Dutch-listed stock and UL is for the UK-listed stock. The material difference is that the dividend from Dutch-listed stock is subject to Dutch tax law and the dividend from UK-listed stock is subject to UK tax law. From practical standpoints, because of the different withholding, UN seems to have greater tax burden than UL which resulted in UL typically traded at higher price than UN. A similar situation is Royal Dutch Shell, RDS.A is subject to Dutch and RDS.B UK dividend rules. Exchanges rates between three currencies (USD, EUR, GBP) might have impacts, too.