General Differences

Little things that are different between the final and beta, but can't be slotted in anywhere else.

 In the beta, the players' cloaks are flat shaded, but are shaded and realistic in the final.

The beta supplies you with ten Tries in two-player mode, but the final only gives you six.

Pressing Start in the beta does not pause the game, but instead pauses your character's animation, and lets you fly around at will, like the debug modes in the Sonic the Hedgehog games! However, it doesn't appear to serve any other purpose than making getting about easier.

Pressing A, B, C, and Start all at once returns you to the main menu in the beta. Pressing those does jack in the final.

You simply can't be hurt in the beta. Obviously, you can't have that in the final.

There are no items at all in the beta. Guess how they changed this in the final.

There's a severe lack of sound effects in the beta.

If a player goes off the bottom of the screen in 2-Player mode, there's nothing to indicate they're gone and need help. The final remedies this with a "HELP!" speech bubble.

The default character is Donald when you start a game; in the final, it's Mickey.

You can't crouch and attack, whilst you can in the final.

Donald's sprite is slightly different between the beta and final! In the beta, his feet have light reflecting off them, his bow tie is missing, and he has no consistent outline; the final corrects this by providing him with an outline, giving him his tie, lessening the realism on his feet, and touching up various other things.

Mickey's sprite is also a touch different! It's nothing major, other than some polishing up of a few parts.

Using your cloak is slower in the beta.

Gens+'s ROM info for both the beta and final has the text "I Love Mickey&Donald Fushigina majikku Bokkusu" as the game's title. Those bits of Japanese roughly translate as "Mysterious magic Box". The (W) title is "World of Illusion starringMickeyMouse&DonaldDuck".