A Winner is You!
For some reason or another, the localizers decided to reword “YOU WIN!” to “YOU WON!”, and made the text less thick. It was probably a result of someone’s personal preference, but who knows for sure.
The crying icon changed between the two games. I’m not sure why, the Japanese version on the left seems clearer to me. Maybe they thought kids would be confused and think it meant “rain” or “water” or something?
Catching a Cold
The icon when you have a cold changed. In MOTHER 2, it’s not even really an icon, it’s text that means “cold”. With so little room to write anything, the logical choice for the localization was to use an icon instead.
Poison Poiii sonnn po i sonnnn
The poison icon is also different between the two games. In MOTHER 2, it’s text that says “poison”, while in EarthBound it’s an icon of skull and crossbones.
PK vs. PSI
In MOTHER 2, most of the special psychic techniques use the prefix “PK”, which stands for psychokinesis.
For some reason this was changed in EarthBound – most techniques use the prefix “PSI” instead, which stands for psionics.
This is why they always say “PK Fire” and such in the Smash Bros. games instead of “PSI Fire”.
When you’re possessed by a little ghost during some parts of the game, the ghost is referred to as the “Tiny Li’l Ghost” in EarthBound. In MOTHER 2, it’s more super-literally “Mini-Mini Ghost”.