Caffeine is one of the most used substance all over the world. Ideally it should be consumed as less as possible. Find out English Breakfast Tea vs Irish Coffee caffeine content in the following sections. However English Breakfast Tea Caffeine levels and Irish Coffee Caffeine levels may differ with their brands, quantity of additives used, types of additives used etc. Below we have given you a generalized idea of safe levels of caffeine in English Breakfast Tea vs Irish Coffee, their side effects and benefits.