I'd expect the first one to be the better one, however, theres one problem.
golden sun itself is a coded mess, it runs slow or buggy on so many emulators, among them the much more capable psp ones. i think even my wii has trouble playing golden sun games.
so yeah... generally, the right answer is try your games on both emulators, if the ds2 actually supports gba emulation. one might be better for some games, the other better for others. but never get your hopes up on golden sun cause its just terrible for every emulator