Without mods its definitely the GBA version for the non-bat shit encounter rate, increased exp n' money rates plus the sprint function.
*Copy and pasted from moeman's post on the breath of fire 2 boards*
undefined posted... Ryusui's translation prevails over the added items and anime stills in the GBA port, in my opinion. The important things the GBA version has are either in the fan translation already (B Button dashing) or can be added with some finagling (Increased EXP/zenny).
And yes, I can confirm Ag-Up does work on the GBA port.
This is a detailed list of changes between BoFII SNES and BoFII GBA.
Text changes:
SNES ..................... GBA
---- ..................... ---
PileWm ................... Porgy
Keep ..................... CHRG
Sweh ..................... SWCH
Wepn for a dancerfighter . Wepn for a fighter
Equip lod/bait............ Equip rod/bait
Gameplay changes:
- 2x experience and 3x zenny won per fight
- Auto-dash function
- Suspend save function
- Spell "Ag-Up" (Agility Up) is fixed and properly temporarily raises Agility
- Several new anime-style stills by Tatsuya Yoshikawa
- New menu portraits, also by Yoshikawa
- New title screen with an orange flame effect
- New title logo
- Redesigned battle menu interface (Looks similar to BoFIV's)
- Redesigned main menu interface
- Typewriter sound effect while dialogue scrolls
- Brighter graphics to suit the original, non-backlit GBA
- Slightly poorer music quality
- New "Exchange" option on the title menu--trade items with another player
by using a link cable
- Minor bug when picking up food in the item creation mini-game; sometimes, the
game will have you talk to the chef's husband instead of pick up your item.
If that happens, you'll have to press the A Button twice to receive your
creations
- Another bug where you can access Night Rider Island early by sailing toward
it and getting off on an invisible beach
- 5 new items, gotten randomly from Exchange: SoulArms, SoulSprd (Soul Spread),
SoulRobe, E.Bean (Energy Bean), and M.Bean (Magic Bean)
The SNES version sounds way better and looks a good deal better since the GBA versions's brighter color palette was meant for the non-backlight GBA. With mods the SNES version would be better. I personally would not bother playing the OG version on nintendo switch online thats for sure.