Which Flashcard?

So I'm researching this topic the whole night by now, and the result is nothing but confusion.

I'm planning to buy a flashcard for my New3DSXL (9.9.0-26E), but I don't know which one to take.
So it seems like Gateway and R4i are the most common ones, but Ican't find no clear informations about the specifications.

I need a Flashcard, that I can play both 3DS and DS games with; features like GBAemu and Online support would be nice.

Thanks for help