For the time being,there are four flash kit can support 3ds roms,they are ,gateway 3ds, r4i gold 3ds deluxe edition , 3dslink and mt-card.Both of these cards can just support 3ds games on N3DS V4.5-4.1, so if you want a card for 3ds roms supporting, check your N3DS/XL firmware version first, if your N3DS firmware stayed on v4.5-4.1, then you can buy mt-card, after all, it was the world first card to support multi 3ds rom.

If all you want is playing nds games or homebrew, then you can choose r4i gold 3ds, this is the most famous card,uses wood firmware,with a quicker updating and 100% game compatibility.

If all you want is playing gba games,then choose dstwo,it comes with gba emulator,and it was the best slot_1 card as well.

In all, currently,there were not any cards can support both 3ds roms, gba/nds roms at one time,but your can buy dstwo to play both nds and gba games without any extra item.