The question in the link you gave talks about naming of JavaScript variables, not about file naming, so forget about that for the context in which you ask your question.
As to file naming, it is purely a matter of preference and taste. I prefer naming files with hyphens because then I don't have to reach for the shift key, as I do when dealing with camelCase file names; and because I don't have to worry about differences between Windows and Linux file names (Windows file names are case-insensitive, at least through XP).
So the answer, like so many, is "it depends" or "it's up to you."
The one rule you should follow is to be consistent in the convention you choose.