As you say, seems a little strange nobody else has mentioned it. As a guess, I'd say that at some point, they increased the fuze size to cut down on the number of failed chargers having to be repaired under warrentee. I also suspect that the current differential between the 2 fuzes was deemed neither dangerous or critical, and would imagine that you could use either one. Of course, you would expect that the 500 ma fuze would be more likely to fail sooner, even with all design and operating specs in tolerence.

As an aside, my Marantz charger failed after about 2 and a half years. I was pretty sure it was the fuze, but with a 3 year warrantee, I let Marantz repair/replace without doing it myself. If a larger fuze had been installed, it might not have failed.