From a genealogical point of view, only the following information is of genuine interest:
Of the three categories, the most useful is probably the marriage entry, because in providing fathers names it gives a direct link to the preceding generation, and it is the easiest to identify from the indexes. Birth entries are much more difficult to identify correctly from the indexes without precise information about date and place, and even with such information, the high concentrations of people of the same surname within particular localities of the country can make it difficult to be sure that a particular birth registration is the relevant one.
Unlike many other countries, death records in Ireland are not very useful for genealogical purposes; there was no obligation to record family information, and the age at death is often very imprecise. This much said, these records can sometimes be of value. The person present at death was often a family member, and the relationship is sometimes specified in the register entry. Even the age recorded may be useful, since it at least gives an idea of how old the person was thought to be by family or neighbours.