Just because you can view a screen with each event, and the fact that events are kept in order (assuming the date/time on your camera is correct), I prefer the event method of organizing in iPhoto. You can also easily edit metadata for everything in an event by right-clickign the event. It's kind of like iTunes (which is a dirty word for lots of Windows users for some reason, but it works for me) in that the original picture isn't edited, but it's stored in a library database/metafile archive.
Folders, to me, are some sort of quasi-album feature that makes exporting easier, but doesn't really do anything for the library at large. I prefer to let iPhoto do most of the grunt work.
I do not understand what I do. For what I want to do, I do not do. But what I hate, I do.