Chicken Little has one of those plots that has me convinced that the writers had a few short days to write it, and-instead of having an outline and a plan and all that jazz-they just wrote the script from the opening to the ending without stopping. The movie goes all over the place and seemingly has no end goal in mind. I think that's why I love it so much.
That's really it, some peoples just prefer what they were introduce as kid, or think Eggman sound dumb/childish and thus stick with the more "cool" name made-up in the west.
Note that I like both names, but some peoples take the matter wayyyyy too seriously....then again, that's the Sonic fanbase for ya.