if you have update your 3ds or 3ds xl console to the latest firmware V6.1.0-11U and you want to buy a 3ds flashcart to work on it. then you need to buy a cart which can work on the latest 3ds firmware because not all the carts currently can work on it.
there are tons of different r4 cards on the market and which r4 3ds card is the best for 3ds V6.1.0-11U Console. the answer is r4i gold 3ds
i recommend r4i gold 3ds card for 3ds V6.1.0-11U because it has been confirmed that this card is working great on the latest 3ds firmware, i say r4i gold 3ds card is the best r4 3ds card because it is really a better card than other cards, much better.
with wood firmware, you can use r4i gold 3ds card to play nearly all the ds games. the wood firmware updates regularly, so you can always play the new games. another, r4i gold 3ds is always working on the latest 3ds firmware and also upgradable to work on the future new 3ds firmware.
In the end, if you plan to buy r4i gold 3ds, make sure you buy a pre flashed one, which means it can work on the latest 3ds firmware out of box, so you don't need to get a ds lite to update it.