it depends on what game do you want to play. if you want to play ds games most, then choose r4i gold 3ds, if GBA games , then dstwo is your best chocie.
If you're willing to pay twice as much, you can go for a SuperCard DSTwo. Updates are also quick, and it runs on it's own firmware (EOS), which has just as much compatibility as wood. But what makes it pricier is all of the extra functions it has: a gba emulator, ability to create save-states, free-cheat, etc. If you're fine without those, you might as well buy the r4i gold. r4i gold 3ds is the most famous slot_1 card for NDS games
This is the best r4 card, uses famous wood firmware,with a quicker updating, can support almost all latest nds games,such as pokemon black 2, pokemon white 2 and so on.
there is no wonder dstwo is the best choice. It was the best slot_1 card,we can use it play gba games and nds games on all nintendo console. Though the price is most expensive,yet,it will never fail to you.
If you still be interested in GBA games, you can choose the no wonder supercard dstwo which allow to play DS games and GBA too. To regard that it's a little expensive. If you are happy on playing DS games, R4i gold 3ds is ok which is high quality and used to play DS games with ok.