Unfortunately, I have to quit Dragon Quest 3 SFC (with English patch) due to a rather serious bug: If you create too many characters, the game may crash on loading a save, before you regain control.
If you want a reasonably bug free version of Dragon Quest 3, and aren't considering the phone or later releases, your two options are as follows:
1. The SFC version *without* the translation patch. This version, of course, is in Japanese, but it has superior graphics and audio, cursor memory of spells cast outside of combat, and better view compared to the GBC version. There is, however, a known bug that can resuit in item duplication, but I am not sure what triggers it (apparently it involves moving the Magic Key in the bag, something that it is never necessary to do).
2. The English GBC version (under the title Dragon Warrior 3). This version has the most content, is in English, and the only significant bug is triggered by losing stats while playing Pachisi. That bug can be avoided by resetting if a stat goes down or by using a throwaway character (as the bug only affects the character who triggers it), and someone posted a Game Genie code that would fix that bug. Note that the Japanese GBC version is not a good choice; there is a memory corruption bug involving the inventory that could easily be triggered by accident (just use a Chimera Wing, cancel out of it, and do some inventory manipulation) and which could softlock you by destroying something important.
Note that the original version of the game (on the Famicom and its NES counterpart) is not a good choice here, as there are many bugs, including the well-known Parry/Fight bug (if you have somebody parry, then cancel the command), the character still gets the defense boost that round. One nasty bug is that, if you create too many characters, the Hero will learn a few combat spells, but will be forever unable to use those spells outside of combat; this list includes Return, which is a spell that you will rarely (if ever) use during combat, but will really want to use outside of combat.