Overall, it appears that the GBA version of Mother 1 is like our EarthBound Zero but with Japanese text. Many small changes to the game when it was localized as EB0, and those changes are now incorporated into the new Mother 1. So for Japanese fans this is a little bit of an upgraded version of Mother 1. Thanks to Mother Online for taking the time to document the changes!

Here is a small list of the changes between the Famicom Mother 1 and the GBA Mother 1:

• The screen animates when you learn a melody.
• The order you learn PSI in is different.
• Your dad doesn't tell you to hold reset when you shut off the game. The GBA doesn't require this, so it was taken out.
• The L-button the GBA acts like the L-button does in the SNES Mother 2/EarthBound.
• The game can be put into sleep mode, just like most other GBA games.
• You don't walk in single-tile increments anymore; movement is more fluid like in Mother 2/EarthBound.
• You can run with the R button. But unlike EB0, the entire game doesn't speed up when you dash.
• There's a mosaic effect when you enter a battle.
• There's no "Map" item. It's missing from EB0 too.
• You can change battle text speed.
• When you check an enemy, you get also get a 1-line comment about that enemy now.
• SMAAAASH!! is always displayed in green. In the Famicom version it would be one of several colors.
• Enemy and ally attack sounds are mixed up. Could be a mistake.
• The text itself changes color when your status changes. Before the color around the text would change while the text itself would remain the same color.
• Enemy enounter rate seems to be much higher. The old trick where you could open the menu often to avoid enemies doesn't work anymore.
• The old strip club is changed to a different kind of shop.
• "Repel Ring" has been added.
• The underground path beneath Magicant is completely different. But it's the same as it is in EB0.
• You can withdraw money from Queen Mary's spring. This was in EB0, however.
• The "Friendship Ring" is gone. It was gone in EB0 as well.
• The Dragon Quest (Dragon Warrior) reference was replaced with "that game".
• Using "Check" in the field will tell you if you might be attacked or not. Useful since it's not exactly clear where town boundaries end.
• Crosses were replaced with simple gravestones, etc. These changes were first seen in EarthBound Zero.
• The crows don't have cigarettes. This change was made when EB0 was first localized.
• The Shroudly doesn't have blood dripping from it's hand, which was also in EB0.
• The Gang/Nasty Zombies don't have blood, but have a tie, also in EB0.
• Dr. Distorto doesn't have blood on his coat, which also was in EB0.
• Enemies appear in the tunnels. This was in EB0.
• Ana is put into character slot #2, moving Loid (who was there first) to slot #3.
• Teleportation time is a little longer, but the speed is a little slower.
• The screen scrolls when you're sucked into the whirlpool. Possibly because of limited screen size.
• A short scene showing everyone escape from Eve's factory was added.
• After you get Eve's melody, you also get a "Memory Chip". It's a useful item that will instantly take you back to Eve.
• The BB (blah blah) gang's boss doesn't hold a knife.
• The Flea Bag doesn't work on enemies like R7038.
• The healer restores your HP. He does this too in EB0.
• After collecting the 7th melody you have to go back to Queen Mary yourself. In the Famicom version you were instantly taken to her, but in EB0 you had to go yourself.
• The philosopher's song is a Japanese translation of what he says in EB0.
• Giegue's attack sound is a little bit off.
• "Run" is replaced by "Sing" late in the game. The blank spot was taken by "Settings" so something had to be replaced.
• An extra area was added right before the final battle.
• The ending is completely different. It's the same as EarthBound Zero's ending.

There aren't too many obvious changes between the SFC and GBA Mother 2 games, but there do seem to be a few, mostly bugfixes.

• The Rock Candy/condiment glitch has been removed.
• In Burglin Park, a person talks about flies landing on the food and making it tastier. The text here was altered very slightly in the GBA version.
• You can't use the Exit Mouse in the Cave of the Past in the GBA port. This was a bug in the SFC version and apparently fixed in EarthBound.
• The Shattered Men in the Summers Museum disappear after you beat Giygas. In the original games, they would still be there if you avoided them earlier on. The game would also mess up if you died against them after beating Giygas.