As both a reader and a researcher I love footnotes. I love the ability to digress slightly, relate related, even if not especially pertinent information, to explain minutiae of an argument without detracting from the narrative. They are also extremely useful for noting where certain information, especially primary information and obscure facts, come from. For scholars, especially respected ones, to simply state a fact as true without acknowledging or explaining where this information comes from is simply unacceptable to me.1
The same information may be expressed in an endnote, but I find them to be unwieldy. In a footnote you may explain tangents, but they must be narrower in scope simply because there should be more text on a given page than footnotes. In theory the same could apply to end-notes, but there is more freedom to ramble on.
As a reader, I hate end-notes because they interrupt the flow of my reading.2 Reading footnotes I can pause at a paragraph break, skim through the footnote and pick up again with little time lost. End-notes I can stop at a paragraph, but then have to find where in the notes at the end of the book my particular note is located. This is even more true when the author renumbers their end-notes by chapter, because then if I reach the right number, I may not be on the right page.
There it is. End-notes are better than no notes, but inferior to footnotes because of reading flow and their lack of checks on their length or deviation.
1 Most recently I saw this in Paul Cartledge’s book Alexander the Great, where he chose a starting point for much of the action with the claim that Parmenion was from Upper Macedonia. My research does not support this, if for no other reason than that Parmenion was a major player in Lower Macedonia for years prior to unification and that there are no sources attributing to his birth location. My suspicion is that he was a middling aristocrat from Lower Macedonia. Further, Upper Macedonia is the modern term for several different principalities, not one unified area. I could go on into much more detail, but that is another footnote.
2 That is if I care enough to follow through.