The ports (GBC and SNES ) of Dragon Warrior III differ in graphics. The GBC version also has Monster Medals, which the SNES version does not. Various class, item, and enemy names differ between all three versions.
Differences from the NES version
Graphic overhaul (all sprites are different).
Thief class .
About 80 addtional weapons and armor .
Bonus dungeon with 8 new Monster and Boss
Pachisi board game.
Personalities .
Tiny/Small Medals.
Pots, barrels, bookshelves, etc can now be searched.
Climb into wells.
Bag added which acts as a vault.
Names of characters and bag can be changed at Tower of Dharma.
New spells added for Merchants and Jesters.
Some monsters have their stats and drop changed.
Boss Troll is no longer a random encounter.
Monster Medals (GBC only).
Second bonus dungeon for GBC with bosses and mimics.
Naming differences
Class differences
NES
GBC
SNES
Goof-Off
Jester
Jester
Merchant
Dealer
Dealer
Pilgrim
Cleric
Cleric
N/A
Thief
Thief
Wizard
Mage
Mage
Medal differences
NES
GBC
SNES
N/A
TinyMedal
Small Medal
Equipment differences
NES
GBC
SNES
Wayfarer's Clothes
?
Traveler Clothes
Leather Helmet
?
Leather Hat
Half Plate Armor
?
Iron Armor
Thorn Whip
?
Spiny Whip
Animal Suit
?
Plush Suit
Poison Needle
?
Poison Dagger
Location differences
NES
GBC
SNES
Tower of Najima
Najimi Tower
Tower of Najima