SD Card
what about pokemon XY and animal crossing NL? will we need to backup the nand after every save?
SD Card

The save is not stored on the console's NAND, but on the Cartridge's NAND.

there are two cartridge type:
One with a ROM + limited size EEPROM for saves, and one with NAND (game data and save are located on the same chipset which can be rewritten to store the saves).
They are more expensive to produce, but can store more data for the save file. it's useful for games with a lot of data to be saved, like Animal crossing.
There's a thread where the differences are explained:
http://gbatemp.net/threads/wth-slc-nand-nand-saving-ap.356852/

Nice to know!
Thx to all who answered me!
Someone asked about Pokemon X/Y. I know the cartridge has a NAND and it's stored there, but what about the eShop version. Is the save still stored in the SD card?
Cheers!

Still SD.
However save verification data is on the NAND
Not only for NAND-saved games but for any game with Anti-savegame restore.Sorry for so many questions. I'm just trying to be on the safe side.
Meaning I still have to, at least, backup once I buy the game?
Since the verification is on the NAND and the actual save in on the SD, if I don't backup the NAND after I bought (after the save is created, meaning starting the game ) the Pokemon, the save itself would be useless, right?
So for NAND saved games bought on eShop I have to backup the NAND at least once to have the save verification saved too.
Thanks!

Not only for NAND-saved games but for any game with Anti-savegame restore.

I have a question, still i dont know if it belongs here. I played Pokemon Y on my 3ds and it upated my FW to the latest release. With this being said, will a gateway card work on my 3ds or do i need a non upgraded ds to insert the card and than put on my 3ds? And if not, i see some of you talking about downgrade. Is it possible to downgrade from 6.2 to 4.5?

I have a question, still i dont know if it belongs here. I played Pokemon Y on my 3ds and it upated my FW to the latest release. With this being said, will a gateway card work on my 3ds or do i need a non upgraded ds to insert the card and than put on my 3ds? And if not, i see some of you talking about downgrade. Is it possible to downgrade from 6.2 to 4.5?

Just curious, has anyone compared a dump made by the gateway 2.0 beta to one taken manually?
You don't need Gateway to use their menu for NAND backuping, you only need some way to launch *.nds file for exploit (old r4i do the trick).Good one!
I thought the same but I could not test as my Gateway is taking forever to arrive...

You don't need Gateway to use their menu for NAND backuping, you only need some way to launch *.nds file for exploit (old r4i do the trick).
Just curious, has anyone compared a dump made by the gateway 2.0 beta to one taken manually?