was wondering which one to buy and where to buy?
AKAIO dev confirmed the AK2i ran out of space for updates, so they can't fit all the data that's needed now.If you have money to burn get the DSTwo. Otherwise, go for the R4i Gold.
The Acekard 2i used to be a good card as well but so far the team hasn't been able to crack latest 3DS protection (either that or they gave up on the card, because no updates).