There shouldn't be any difference between the two versions, but the game was developed mainly with the original Game Boy in mind. Mostly I've seen people emulate the GB version for streaming.
Thanks for the quick reply! I've done some testing, and at least OnionOS for the Miyoo only recognizes the .gb file, so I'll use that one.
I also started to play Batty Zabella and I like it very much! Especially the humor, which IMO is one of the most difficult parts in a game to get right.
Actually, it's also my first Gameboy Game ever, because I never owned a GB and thus, also never emulated one. But I think they're perfect for the modern emulation handhelds, and thus, when I stumbled upon your very appealing GB game, I took the opportunity. And I haven't been disappointed. Thanks for supporting the GB world up until today!:D