In a string below re Malew MIs, David D reminds us that sometimes the extra info we find on the burial register can be something that helps us to identify a surname line in a particular parish.
One of the most common extra pieces of info is indication of residence. Particularly, in the earlier times 1700's-early 1800's when we usually don't find many MIs, indication of residence can help separate out some of the Johns, Marys, etc.
The online burial info usually doesn't contain the extra tidbits but they can be found in the IOMFHS pubs and/or the actual microfilms.
Other tidbits include died of smallpox, cholera; infant; child of X; etc.
The IOMFHS pubs make it easy to survey a particular surname and look for place of residence. Often this info, together with will, land records can be helpful in figuring out which is the line you're looking for.
You do have to be flexible with spelling not only the surname but also the residence.
Donna