The audio tracks are the same, except for track one. Take this with a grain of salt, as I don't have an original disc to check and the iso could be f'd up.
I noticed very few visual changes (pretty much limited to translations), but here's what I saw:
- "Seagull Stage" is renamed "River Stage".
- Buddies say "Good Luck" instead of "Bye Bye" at end of levels.
- Sign says "Next Stage" instead of "Go To Next" at end of levels.
In other words, the differences are minimal.
P.S. - This was an interesting experience. I had two simultaneous instances of Mednafen running the two different isos and controlled two zonks at once. Definitely an odd way to play a game, eh?